NOM-023-STPS-2012, Underground and open-pit mines - Occupational safety and health conditions

That on 24 April 2012, in compliance with Article 46, section I, of the Federal Law on Metrology and Standardisation, the Ministry of Labour and Social Welfare (Secretaría del Trabajo y Previsión Social, STPS) submitted to the National Consultative Committee for Standardisation of Occupational Safety and Health the Preliminary Draft of Amendment to this Official Mexican Standard, and that Committee considered it correct and agreed that it be published as a Draft in the Official Gazette of the Federation (Diario Oficial de la Federación, DOF); That to comply with Articles 69-E and 69-H of the Federal Law of Administrative Procedure, the corresponding Preliminary Draft was submitted for consideration to the Federal Commission for Regulatory Improvement, which issued a favourable opinion on it; That on 18 May 2012, in compliance with the Agreement establishing the organisation and Rules of Operation of the National Consultative Committee for Standardisation of Occupational Safety and Health, and with Article 47, section I, of the Federal Law on Metrology and Standardisation, the Draft Amendment to Official Mexican Standard NOM-023-STPS-2003, Work in mines - Occupational safety and health conditions, to become PROY-NOM-023-STPS-2012, Underground mines and open-pit mines - Occupational safety and health conditions, was published in the Official Gazette of the Federation, so that, within the 60 calendar days following that publication, interested parties could submit their comments to the Committee; That having received comments from four proponents, the Committee proceeded to study them and resolved on them in due course, this authority publishing the respective responses in the Official Gazette of the Federation of 6 September 2012, in compliance with Article 47, section III, of the Federal Law on Metrology and Standardisation; That as a result of incorporating the comments submitted on the Draft Amendment to Official Mexican Standard NOM-023-STPS-2003, Work in mines - Occupational safety and health conditions, to become PROY-NOM-023-STPS-2012, Underground mines and open-pit mines - Occupational safety and health conditions, as well as of the final review of the draft itself, various modifications were made for the purpose of giving clarity, consistency and legal certainty to the provisions applicable in workplaces, and That in view of the foregoing considerations and given that the National Consultative Committee for Standardisation of Occupational Safety and Health granted its respective approval, the following is hereby issued: OFFICIAL MEXICAN STANDARD NOM-023-STPS-2012, UNDERGROUND MINES AND OPEN-PIT MINES - OCCUPATIONAL SAFETY AND HEALTH CONDITIONS

To establish the minimum occupational safety and health requirements to prevent risks to workers who carry out activities in underground mines and open-pit mines.

2.1 This Official Mexican Standard applies throughout the national territory and to all workplaces where activities related to exploration and extraction in underground or open-pit mining operations are carried out, regardless of the type and scale of the workplace concerned.

2.2 The following are exempt from compliance with this Standard: a) Workplaces where activities related to exploration and extraction are carried out to obtain, as main products: 1) Petroleum; 2) Natural gas, or 3) Substances contained in suspension or dissolved in groundwater or injected into the subsoil; b) Underground mines where activities related to the exploration and/or extraction of coal and of gas associated with such deposits are carried out, or c) Mines where activities related to the exploration and/or extraction of radioactive minerals are carried out.

For the correct interpretation of this Standard, the following applicable official Mexican standards, or those that replace them, shall be consulted:

3.1 NOM-002-STPS-2010, Safety conditions - Fire prevention and protection in the workplace.

3.2 NOM-010-STPS-1999, Safety and hygiene conditions in workplaces where chemical substances capable of generating contamination in the working environment are handled, transported, processed or stored.

3.3 NOM-011-STPS-2001, Safety and hygiene conditions in workplaces where noise is generated.

3.4 NOM-015-STPS-2001, Elevated or reduced thermal conditions - Safety and hygiene conditions.

3.5 NOM-017-STPS-2008, Personal protective equipment - Selection, use and handling in the workplace.

3.6 NOM-018-STPS-2000, System for the identification and communication of hazards and risks from hazardous chemical substances in the workplace.

3.7 NOM-019-STPS-2011, Constitution, composition, organisation and operation of safety and hygiene committees.

3.8 NOM-020-STPS-2011, Pressure vessels, cryogenic vessels and steam generators or boilers - Operation - Safety conditions.

3.9 NOM-021-STPS-1993, Concerning the requirements and characteristics of reports on occupational risks that occur, for compiling statistics.

3.10 NOM-022-STPS-2008, Static electricity in the workplace - Safety conditions.

3.11 NOM-024-STPS-2001, Vibration - Safety and hygiene conditions in the workplace.

3.12 NOM-026-STPS-2008, Safety and hygiene colours and signals, and identification of risks from fluids conveyed in pipelines.

3.13 NOM-027-STPS-2008, Welding and cutting activities - Safety and hygiene conditions.

3.14 NOM-029-STPS-2011, Maintenance of electrical installations in the workplace - Safety conditions.

3.15 NOM-030-STPS-2009, Occupational safety and health prevention services - Functions and activities.

3.16 NOM-031-STPS-2011, Construction - Occupational safety and health conditions.

For the purposes of this Standard, the following definitions are established:

4.1 Timbering; structural support: The means for stabilising the roof and walls of a gallery or mine working by means of a support system, whether sets, rock bolting, shotcrete or any other system that fulfils that function.

4.2 Scaling: The act of testing the walls, roof and face of a working or gallery with an iron bar, to bring down loosely adhered rock that may pose a risk to personnel.

4.3 Angle of repose of material: The angle that allows the stability of strata or piles of material.

4.4 Labour Authority; Employment Authority: The competent administrative units of STPS that perform inspection functions in respect of occupational safety and health, and the corresponding units of the federative entities and the Federal District that act in support of them.

4.5 Self-rescuer: The personal respiratory protection device designed for escape from atmospheres with carbon monoxide concentrations of up to 1 per cent.

4.6 Bench, step: The layer of mineral that is worked at the same height and level.

4.7 Blastholes: The holes drilled in which explosive charges are placed for breaking material.

4.8 Misfired charges: Explosive charges that have not detonated after blasting has taken place.

4.9 Man-cage; cage: The lift used for the vertical transport of workers and materials.

4.10 Emergency situation: The possible occurrence of fires, explosions, spills, floods, poisonings and/or collapses.

4.11 Workplace: All such places as buildings, premises, facilities and areas where production, marketing, transport and storage activities or the provision of services are carried out, or in which persons subject to an employment relationship work.

4.12 Personal protective equipment (PPE): The set of elements and devices for personal use to protect the worker from accidents and illnesses that may be caused by agents or factors generated in the course of carrying out their activities, and which, according to the risk to which workers are exposed, may be basic or specific. Where the risk analysis establishes the need to use work clothing with specific protective characteristics, such clothing shall be considered personal protective equipment.

4.13 Cable ladders; ladders: Two parallel cables with metal or wooden rungs, used as ladders.

4.14 Waste dump; tip: The place where materials resulting from excavation in a mine are deposited, excluding tailings.

4.15 To produce: The act of presenting records and/or documents for review, by any means, electronic or printed, to the labour authority that requests them, to verify compliance with the requirements set out in this Standard.

4.16 Exploration: The works and activities carried out to identify material deposits and to quantify and evaluate their content.

4.17 Extraction: The works and activities aimed at the preparation and development of the area containing the mineral deposit, as well as those aimed at breaking and extracting materials in a mine.

4.18 Ground support: The reinforcement of the roof, floor and walls of a mine working by means of any structural support system.

4.19 Face: The exposed wall of the gallery on which the mineral is broken.

4.20 Longwall face: The exposed face of variable length on which mineral is broken, bounded by two adjacent workings or galleries.

4.21 Gallery: The working made in underground mines for mineral extraction, ventilation, communication or drainage.

4.22 Incident: An unexpected event in which no injuries or damage to the physical integrity or health of workers occur.

4.23 Hoist: Equipment that, by means of one or more steel cables, enables the movement of buckets, cars and cages to transport workers, materials and equipment.

4.24 Major machinery; major mobile equipment: High-tonnage equipment, such as jumbos, mechanised scaling machines, load-haul-dump vehicles (scooptrams), low-profile trucks, continuous miners, rock bolters, long-hole drilling equipment, in the case of underground mines, and off-highway trucks, power shovels, draglines, loaders, drills, tractors (bulldozers) and motor graders, in the case of open-pit mines.

4.25 Mine: An excavation made to extract minerals by means of shafts and galleries or in the open pit.

4.26 Employer: The individual or legal entity responsible for exploration and extraction activities in underground or open-pit mining operations.

4.27 Blaster: The worker trained and authorised by the employer to use explosives.

4.28 Occupationally Exposed Personnel (OEP): Workers who, in the course of their work activities, are present in a working environment where a higher-impact risk exists, or who carry out a hazardous activity.

4.29 Safety procedure; safe work procedure: Written instructions, detailed and sequential, for carrying out an activity with the least risk to workers and the workplace. It is set out in documents containing the purpose and scope of the activity; the manner in which it shall be carried out; the identification of hazards, risks and possible injuries, as well as the protective equipment to be used; the functions and/or responsibilities of the workers involved, as well as the materials, equipment or work implements that are to be used, controlled and recorded.

4.30 Stope: The underground mine excavation, either above or below the level of a gallery.

4.31 Risk: The combination of the probability of occurrence of a hazardous event or exposure and the severity of the harm or health impairment that the event or exposure may cause.

4.32 Serious risk: A risk that may compromise the physical integrity and/or life of workers and/or cause damage to the workplace facilities, where the corresponding safety requirements and conditions are not observed.

4.33 Imminent risk: A risk that evidently compromises the physical integrity and/or life of workers, owing to failure to comply with the safety conditions provided for in this Standard, and that requires immediate attention.

4.34 Occupational safety and health prevention services: Those provided by trained personnel - internal, external or mixed - whose main purpose is to prevent occupational accidents and illnesses, through compliance with occupational safety and health regulations. Internal services are understood to be those provided by the employer or mine personnel; external services, those provided by personnel independent of the mine, and mixed services, those provided both by internal personnel and by personnel independent of those working in the mine.

4.35 Open pit: The open-pit mine working used to extract various minerals.

4.36 Shaft: The vertical or inclined conduit of a mine working through which workers, materials and equipment ascend and descend.

4.37 Receiving hopper: The large-capacity storage unit for containing and regulating the flow of materials.

4.38 Verification unit: The individual or legal entity accredited and approved under the terms of the Federal Law on Metrology and Standardisation, to verify the degree of compliance with this Standard.

4.39 Mining unit: One or more mines operated under the same technical and administrative management.

4.40 Blasting; shot; firing: The act of blasting the mine working face with explosives.

5.1 Have the risk analysis for hazard identification and risk control, in accordance with Chapter 7 of this Standard.

5.2 Have, where applicable, a study ensuring that self-rescuers enable workers to reach the surface from the most remote point of the underground mine, or to take refuge in a safe shelter, and, where applicable, reserve or additional self-rescuers, in accordance with the following: a) Provide one self-rescuer for each worker present inside the mine; b) Distribute reserve or additional self-rescuers at strategic locations; c) Mark the strategic locations where reserve or additional self-rescuers are kept with reflective or fluorescent materials, and d) Identify the strategic locations where reserve or additional self-rescuers are kept on a plan for the information of all personnel.

5.3 Draw up and follow up a programme for the inspection and maintenance of the equipment, machinery and/or vehicles used, which shall contain at least the scheduled date, the activity to be carried out, the date it is carried out and the person responsible for its execution.

5.4 Have available the safety procedures for carrying out exploration and extraction activities, drawn up in the Spanish language.

5.5 Comply with the safety and health requirements, as applicable: a) In underground mines, on the basis of the provisions of Chapter 8 of this Standard, and b) In open-pit mines, in accordance with Chapter 9 of this Standard.

5.6 Designate, as the person responsible for compliance with this Standard, an engineer legally authorised to practise, as provided for in Article 34 of the Mining Law.

5.7 Observe the provisions of the official Mexican occupational safety and health standards issued by STPS that are applicable to the surface facilities of the mining unit, such as offices, personnel services, workshops and warehouses, processing plants, tailings dams, among others.

5.8 Carry out an inspection of the safety conditions of the working faces in underground mines and of the pits in open-pit mines, at each work shift, and keep a record of the results of the inspections, which shall record the signatures of the outgoing and incoming shift supervisors. The inspection to ensure worker safety shall consider, at least, the following: a) In underground mines, the safety conditions relating to ground support, ventilation and the equipment used for breaking material, and b) In open-pit mines, the safety conditions relating to the stability of the slopes and the major machinery.

5.9 Have a system for recording, for each work shift, the entry and exit of workers from the underground mine, as well as identifying their location by area or zone on a plan at all times, preferably in real time.

5.10 Install and keep available shelters inside underground mines, as determined by clause 8.14 of this Standard.

5.11 Have safety data sheets (SDS) for all hazardous chemical substances used, and identify the tanks, containers and areas that contain them or their waste, in accordance with NOM-018-STPS-2000, or the standard that replaces it.

5.12 Constitute, form and organise the safety and hygiene committee(s) and supervise their operation, in accordance with NOM-019-STPS-2011, or the standard that replaces it.

5.13 Observe the provisions of NOM-020-STPS-2011, or the standard that replaces it, in respect of pressure vessels, cryogenic vessels and steam generators or boilers.

5.14 Notify STPS of occupational accidents that occur in the workplace, on the basis of the provisions of NOM-021-STPS-1993, or the standard that replaces it.

5.15 Have, in the areas of the mining units, prohibition, mandatory action, caution and information signage, as applicable, in accordance with NOM-026-STPS-2008, or the standard that replaces it, to indicate: a) The risks in each area of the mining unit; b) The use of personal protective equipment, and c) The evacuation routes, with elements indicating the direction of the exit, as well as safety signs or notices bearing, where applicable, reflective or fluorescent materials.

5.16 Carry out welding and cutting activities, as established in NOM-027-STPS-2008, or the standard that replaces it.

5.17 Have the occupational safety and health prevention services referred to in NOM-030- STPS-2009, or the standard that replaces it.

5.18 Carry out the construction of buildings, facilities or premises of the mining unit, in accordance with NOM-031-STPS-2011, or the standard that replaces it.

5.19 Provide workers with basic personal protective equipment, in accordance with Chapter 10 of this Standard, and, where applicable, the specific equipment that corresponds to them, based on the activity they carry out and the risks to which they are exposed.

5.20 Verify that workers use personal protective equipment while carrying out their normal and emergency activities.

5.21 Authorise in writing only workers who have been trained - in accordance with the corresponding safety procedures - for the receipt, storage, transport, handling and use of explosives, as well as those who operate and maintain locomotives, major machinery, major mobile equipment, electrical installations, vehicles and motorised hoists, in accordance with Chapter 11 of this Standard.

5.22 Have a programme for the health surveillance of workers, as determined by Chapter 12 of this Standard.

5.23 Have an emergency response plan available for consultation and application by workers and emergency emergency response team members, in accordance with Chapter 13 of this Standard.

5.24 Provide workers with hygienic spaces for eating that comply with the provisions of the official Mexican standards issued in this respect by the Ministry of Health.

5.25 Provide workers with drinking water services and sanitary facilities - toilets, urinals, showers, among others - in sufficient quantity, on the basis of the provisions of the official Mexican standards issued in this respect by the Ministry of Health, or the applicable local and environmental legislation.

5.26 Provide occupational safety and health training to all workers, in accordance with the safety procedures relating to the activities they carry out, in accordance with Chapter 14 of this Standard.

5.27 Inform all workers of the mining units of the risks to which they are exposed in relation to the activities they carry out, at least once a year, and inform persons who are not part of the workplace, prior to their entry into the mines for any reason.

5.28 Keep a record of the information provided to all workers, which shall contain at least: the date on which the information was provided; the name and position of the workers to whom it was provided, and the name of the instructor.

5.29 Follow up on reports of incidents, accidents, unsafe conditions and acts, and/or actual or potential emergency situations, detected during the performance of activities. A record shall be kept of the follow-up to reports submitted by the worker or the safety and hygiene committee, which shall contain at least: its description; the area involved; the dates of receipt and attention, and its current status.

5.30 Investigate accidents and disasters that have occurred, to adopt preventive and corrective measures to avoid their recurrence, and keep a record of them, in accordance with Chapter 15 of this Standard.

5.31 Evaluate the conditions of the underground mine or open-pit mine after a disaster has occurred, to authorise, where applicable, the entry of the emergency response teams, and resume activities only once the conditions ensuring worker safety have been re-established.

5.32 Prohibit persons under 18 years of age and pregnant or breastfeeding women from working inside an underground mine or in an open-pit mine.

5.33 Produce to the labour authority, when so requested, the documents that this Standard requires the employer to draw up or hold.

6.1 Comply with the safety procedures for carrying out their activities and, where applicable, for the operation and maintenance of major machinery.

6.2 Check, before starting activities, that machinery, equipment, tools and work implements are in safe and operational condition, and immediately report to the employer any anomaly detected that places the worker at risk during use.

6.3 Use the safety devices installed on machines, equipment, tools, installations and structures, and refrain from arbitrarily connecting, disconnecting, changing or removing these devices.

6.4 Operate and maintain major machinery, major mobile equipment, electrical installations, vehicles and motorised hoists.

6.5 Receive, store, transport, handle or use explosives only when they have received specific training in the matter and have written authorisation from the employer.

6.6 Use and maintain the personal protective equipment provided by the employer, on the basis of the procedures established for that purpose regarding use, inspection, replacement, cleaning, maintenance, storage and final disposal.

6.7 Refrain from carrying out activities that could have, as a direct or indirect consequence, personal accidents and/or material damage, that contravene the provisions of this Standard and those established by the employer.

6.8 Immediately notify the employer and the safety and hygiene committee, in writing, of incidents, accidents, unsafe conditions and acts, and/or actual or potential emergency situations, detected during the performance of their activities.

6.9 Follow the instructions established by the employer under the emergency response plan and, where applicable, provide assistance for as long as required, in the event of an emergency or a situation of imminent risk.

6.10 Undergo the medical examinations required in accordance with their activities and truthfully provide the information requested by the physician conducting the examination.

6.11 Notify the employer, in the case of women who are pregnant, of that condition.

6.12 Attend and participate in the training or information on occupational safety and health provided by the employer.

6.13 Participate in the training and instruction provided by the employer for the operation, maintenance, repair or modification of equipment and, where applicable, tests thereof.

6.14 Participate in the interviews conducted by the labour authority or, where applicable, the verification unit.

7.1 The risk analysis for hazard identification and risk control shall include the determination of the magnitude of risk (MR) and the controls necessary for its prevention, protection and control.

7.2 The risk analysis for hazard identification and risk control shall be: a) Up to date; b) Available to workers, and c) Approved and signed by the employer and the person responsible for the occupational safety and health prevention services.

7.3 The risk analysis for hazard identification and risk control shall be reviewed when: a) The exploration, extraction, ground support, ventilation system or electrical installation processes are modified, as applicable; b) Any change is made that may alter the safety conditions and procedures, and c) The risks to workers or to the workplace are modified.

7.4 The risk analysis for hazard identification and risk control shall consider, as applicable, the following: a) The analysis of activities by process, area or job, comprising at least: 1) Routine and non-routine activities, and 2) The activities of all persons who have access to the workplace, including contractors and visitors; b) Installations that may generate hazards; c) The infrastructure, equipment and materials in the workplace, in particular the safety and operating characteristics and conditions that the machinery, equipment and tools to be used shall meet; d) The hazardous chemical substances handled, such as explosives, fuels and lubricants, among others; e) The recognition, evaluation and control of applicable contaminants of the working environment, in accordance with official Mexican standards NOM-010-STPS-1999, NOM-011-STPS-2001, NOM-015-STPS-2001 and NOM-024-STPS-2001, or the standards that replace them; f) Existing hazards and risk factors, comprising at least: 1) Those corresponding to the work activities; 2) Those capable of affecting the safety and health of persons, and 3) Those originating in the vicinity of the mine from other activities; g) The safety procedures used to carry out the activity; h) Modifications, including temporary changes, and their impact on operations, processes and activities, where applicable, and i) The emergency response plan.

7.5 The risk analysis for hazard identification and risk control shall contain, at least, the following: a) The analysis of the areas, processes and activities throughout the mine; b) The identification of workers and their activities by job, both in normal and emergency conditions; the personal protective equipment, both of workers and of members of the emergency response teams, as well as rescue equipment; c) The identification of the highest-impact risks, owing to their flammability, explosiveness, as well as their effect on health; d) The hazardous activities to which workers are exposed, based on the safety procedures and the provisions to be considered in the emergency response plan; e) The analysis of workers' exposure to the hazards and risk factors existing in the activities of their jobs, both in normal and emergency conditions; f) The result of the evaluation of contaminating agents and their comparison with the applicable exposure limit values, in accordance with official Mexican standards NOM-010-STPS-1999, NOM-011-STPS-2001, NOM-015-STPS-2001 and NOM-024-STPS-2001, or the standards that replace them; g) The determination of risks based on existing hazards, in accordance with the ranking established in clause 7.8 of this Standard; h) The probability of occurrence of risks, in accordance with the statistics of risks that have occurred, and the preventive measure corresponding to each risk; i) The possible impact from the evaluation of the magnitude of the harm that may occur to workers or to the mine; j) The number of events per unit of time that may occur; k) The ranking of risks based on their probability of occurrence and possible impact (magnitude), and l) The proposal of the occupational safety and health procedures and conditions to be implemented for the control of the risks detected.

7.6 The magnitude of risk (MR) shall consider: a) The probability of occurrence of risks (P), which shall be obtained on the basis of the statistics of risks that have occurred in the workplace associated with the mine's activities, and, where such statistics are not available, on the basis of those of other workplaces with similar characteristics, in accordance with the content of Table 1; Table 1 Probability of occurrence of risks (P)

                                             That      exceptionally     may
                      Isolated                                                           1

7.7 The magnitude of risk (MR) shall be obtained by combining the probability of occurrence of the risk with the exposure of workers and the severity of the harm it may cause, applying the following equation: MR = P x E x S where: MR = Magnitude of risk; P = Probability of occurrence of the risk; E = Exposure of workers to the risk, and S = Severity of harm.

7.8 Risks shall be ranked by their magnitude as serious, high, medium, low and minimal. These categories shall serve as the basis for establishing the order of attention of the prevention, protection and control measures to be adopted, in accordance with the provisions of Table 4. Table 4 Risk ranking Result of the Equation Ranking Description MR = PxExS Requires the application of strict and specific safety measures, to modify the conditions Serious Greater than 400 safety; the safety procedures; the personal protective equipment, or training. Requires immediate attention and

7.9 Risks classified as serious shall be attended to immediately and, thereafter and successively, high, medium and low risks and, lastly, minimal risks.

7.10 Activities shall be suspended - immediately - if the results of the evaluation of contaminating agents are above the exposure limit values, until: a) Prevention and control measures are established; b) The new safety procedures are in place; c) The additional personal protective equipment required is determined; d) The contamination values are within the exposure limit values, and e) The emergency response plan is applied, where applicable.

8.1 Studies and plans

8.1.1 Before carrying out work in underground mines, at least the following studies shall be available: a) Geotechnical: rock mechanics or soil mechanics; b) Geological, to locate faults and rock types, and c) Hydrological, to evaluate flood risks, together with the control procedures.

8.1.2 The geotechnical, geological and hydrological studies shall be updated when the original conditions taken into account for their preparation are modified or altered.

8.1.3 The geotechnical, geological and hydrological studies shall be kept for the operational life of the mine.

8.1.4 Underground mines shall have plans of the mining operations that meet the following conditions: a) Be up to date based on the progress of the workings; b) Be approved and signed by the employer and by the person responsible for the preventive occupational safety and health services, and c) Be available at the mine office for consultation by personnel.

8.1.5 The plans of the mining operations shall contain, at a minimum, the following information: a) Longitudinal sections showing the shafts, crosscuts, galleries, exploration and exploitation faces, stopes, backfilled areas and other underground mine workings; b) The surface profile of the mine, with the location of subsidence areas and any known aquifer; c) The location of pumping stations and hoists; d) The ventilation of the mine, showing: 1) The speed and direction of the air; 2) The location of the ventilation equipment; 3) The doors and elements required to control it, and 4) The points of interconnection with other mines; e) The electrical installation, showing the single-line diagram; the load schedules, as well as the voltage of the cabling and of the electrical equipment; f) The location of the fire protection system, specifying the location of: 1) Extinguishers and fixed equipment; 2) Rescue stations; 3) First-aid stations, and 4) Personal protective equipment for emergencies, and g) The location of the mine refuges.

8.2 Excavations and ground support

8.2.1 Underground mines shall have safety procedures for carrying out excavation and ground support work to avoid risks to workers, in accordance with the results of the geotechnical, geological and hydrological studies.

8.2.2 In underground mines, the safety procedures for carrying out excavation and ground support work shall be available for consultation by any worker involved in the activity.

8.2.3 In underground mines, excavation, ground support and inspection activities shall be carried out only by personnel trained and authorised by the employer.

8.2.4 Underground mines shall establish a ground support plan, based on the results of the geotechnical, geological and hydrological studies, which shall consider at least: a) The dimensions of the workings; b) The plans, sections and, where applicable, diagrams of the mine's structural support; c) The design and dimensions of the pillars that will provide protection for the galleries; d) The design criteria and selection of the ground support to be used; e) The face support systems and the specific ground support for development workings and excavations; f) The materials to be used in the structural support; g) Ground support in accordance with the predominant geological conditions for the mine's working method; h) The safety procedures, with the safety measures and/or conditions to be adopted to avoid risks to workers when carrying out excavation and ground support work; i) The control of displacement and the maintenance of the stability of the mine strata, through the support of the roofs and walls of the galleries, to protect workers from hazards and to maintain safety inside the mine; j) The modification of the ground support whenever the predominant geological conditions change; k) The control of roofs by means of ground support, according to the applicable support method, and l) The methods for pillar recovery, when this exploitation method is used.

8.2.5 The safety procedure for carrying out excavation in underground mines shall include, at least, the following: a) The results of the geotechnical, geological and hydrological studies; b) The requirement that only authorised personnel carry out this activity; c) The machinery and equipment to be used; d) The physical properties of the rock materials to be excavated, such as hardness, stability or fracturing; the materials used for backfilling, where applicable, as well as the presence of moisture and clay, among others; e) The safety measures to prevent the excavations from connecting to a source of water or saturated material; f) The type of ground support specific to the characteristics of the rock, and g) The instructions for activating the emergency response plan.

8.2.6 Underground mines shall establish a specific procedure for carrying out workings when excavation is performed with a continuous miner, jumbo or jackleg drill.

8.2.7 The specific procedure for excavation with a continuous miner shall contain, as safety measures, at least the following: a) The planning of activities, specifying the place where cutting will be carried out, the estimated time and the services that will be required; b) The blasting schedules established for other areas of the mine; c) The performance of activities only by personnel trained and authorised for that purpose; d) The safety procedures for operating the continuous miner and the instructions in the equipment manufacturer's manual; e) The work cycles, indicating that the task shall only begin once the ground of the working has been stabilised, by means of bolting and/or shotcrete or any other recommendation established in the rock mechanics study; f) The work cycle, which shall consider at least the following steps: 1) Inspecting the site to verify that the ground is stabilised and in good condition; 2) Checking the equipment, especially the drum picks and, where applicable, replacing them; 3) Carrying out the necessary cuts until the operator's cabin reaches the last line of bolts installed in the previous cycle (see Figure 1); Figure 1 Excavation with a Continuous Miner 4) Withdrawing the continuous miner to a safe location; 5) Scaling the cut area by mechanised means; 6) Removing the scaling debris from the roof and walls of the working; 7) Bolting the working up to the face, based on the established pattern; 8) Carrying out a structural geological survey to recommend, where applicable, any additional reinforcement; 9) Installing the additional reinforcement recommended in the structural geological survey; 10) Applying shotcrete in accordance with the specifications contained in the rock mechanics study, where applicable, and 11) Starting the next cycle; g) Suspending advance whenever the operator leaves the equipment, the power is cut off and a tag and lockout padlock are fitted; h) Carrying out maintenance, inspection and/or repair work in the supported zone only when the equipment is not moving and the operator is outside the cabin, and i) The safety procedures for responding in the event of an emergency, in accordance with the emergency response plan.

8.2.8 The safety procedure for carrying out ground support work shall include, at least, the following: a) The type of ground support installation: manual or mechanised; b) The materials to be used for constructing the ground support; c) The machinery, equipment and tools to be used; d) The sequence of activities in installing the ground support; e) The method of orientation control for maintaining the projected direction of the galleries, when a development working is being supported; f) The safety procedures for installing additional roof support, when galleries have dimensions greater than those of the original design; g) The safety procedures for installing ground support, in the event that geological faults and excessive moisture are identified, which shall consider at least: 1) Instructions on the proper use of tools and, where applicable, of safety devices, and the location, in a safe place, of the persons involved in the operation, and 2) Instructions for carrying out checks each shift, to assess the behaviour and deformation of the ground support resulting from stresses in addition to its strength, and to adopt the corresponding corrective measures, and h) The frequency with which inspections of the ground support shall be carried out.

8.2.9 Underground mines shall have a safety procedure for ground support activities in areas at high risk of rockfall, which shall include, at least, the following: a) The approval of the mining engineers; b) Safety instructions for the use of tools and safety devices; c) The location, in a safe place, of the persons involved in the operation; d) The safety procedures for recovering the materials used, as well as for propping and supporting the roofs and walls of the mines when cave-ins occur, and e) Instructions for carrying out visual inspections each shift, to assess the behaviour and possible deformation of the ground support resulting from stresses in addition to its strength, and to adopt the corresponding corrective measures.

8.2.10 To carry out excavation and ground support activities in underground mines, the following safety measures shall be observed: a) Have at least two independent exits to the surface; b) Place safety signs or notices at abandoned surface excavations, waste dumps or spoil heaps and abandoned underground mine workings, as well as in areas that pose a risk to workers; c) Provide protective measures at shafts to prevent the fall of persons or material; d) Verify that the dimensions and location of the pillars comply with the calculation made on the basis of the rock mechanics study, to avoid endangering the stability of the workings or affecting the surface installations located above them; e) Carry out an inspection before resuming work, in those workings whose operation has been suspended for a period of time, to verify that no hazardous conditions exist in respect of: 1) The ground support; 2) The drainage systems; 3) The traffic surfaces; 4) The atmosphere, owing to the presence of harmful gases or oxygen deficiency that could endanger the life or health of persons, and 5) The location, owing to the presence of harmful fauna or guano; f) Carry out the inspection with at least two workers from each work crew, who shall have, at a minimum: 1) Detectors for oxygen, carbon monoxide and, where applicable, nitrogen dioxide, sulphur dioxide or any gas or explosive material that could be generated during mining, and 2) Appropriate personal protective equipment, and g) Keep a record of the results of the inspections.

8.2.11 The following safety measures shall be adopted when installing ground support: a) Position securely and rest on firm ground - in the case of the use of frames - all the props used to support the roofs or walls of the galleries, and secure them by means of ties or spacers between support frames; b) Distribute the loads adequately over the structure, in accordance with the projected design; c) Install the ground support - in the case of inclined seams - in such a way as to ensure that the loads are supported, taking into account the dip of the seams or the inclination of the galleries and the possible movement of the strata; d) Determine the maximum advance depth on the basis of the rock mechanics study, to support the rock mass, when a continuous miner is used, and e) Check the condition of the ground support, where applicable, and keep a record of the results of the checks, which shall consider at least: 1) The location of the ground support; 2) Its condition; 3) Recommendations for remedying the deficiencies found; 4) The dates of the inspections, and 5) The name of the person responsible for carrying out the inspection.

8.2.12 In areas with water seepage from the roof or walls that affects the stability of the ground, the following shall be done: a) Carry out ongoing checks of the support systems; b) Carry out reinforcement to prevent landslides and deterioration of those mine systems, where applicable, and c) Inspect the areas with seepage and keep a record of the results of the checks, which shall consider at least: 1) A description of the location checked; 2) The conditions detected; 3) The date of the check, and 4) The name of the person who carried out the check.

8.2.13 Access for carrying out any type of work shall be prohibited at those places in the mine that need to be supported, except for the personnel carrying out that activity.

8.3 Installations

8.3.1 The following safety conditions and elements shall be adopted in underground mine workings and installations: a) Have a tunnel, ramp or shaft for the usual access to and exit from the mine, and another independent working, signposted, for emergency exit; b) Protect shafts and workings where a person could fall into a void with structural elements, such as mesh, grilles, walls, bulkheads, among others; c) Provide, where applicable, locks on the doors at shafts, to prevent them from opening unintentionally; d) Provide emergency escape ladders in the shafts used for worker access and exit; e) Protect and signpost cavities or subsidence that form on the surface, to prevent the fall of workers, vehicles and materials; f) Guard and signpost shafts, raises and any type of opening that poses a hazard to workers; g) Place signs and barriers or devices preventing passage into tunnels not intended for worker traffic; h) Provide warning signs and physical guards at the entrance to ventilation systems, to prevent contact with any moving part; i) Have doors fitted with locks in the ventilation systems to prevent them from opening unintentionally; j) Provide lighting of at least 100 lux at: 1) The access points to the shaft headframe buildings; 2) The shaft stations or landings; 3) The hoist rooms; 4) The drive unit of the conveyors used to move materials; 5) The electrical substations; 6) The pumping stations and general discharge hoppers, and 7) Other fixed installations containing machinery; k) Prohibit the storage of lubricants and fuels outside underground mines at a distance of less than 50 metres from the shafts; l) Locate maintenance workshops and other installations providing services to underground mines at a distance of more than 20 metres from lubricant and fuel storage areas; m) Place hoist rooms at a safe distance, established in accordance with the requirements specific to cable winding, in the case of drum hoists, and, in the case of friction hoists, the rooms shall be located above the shaft collars; n) Protect with stops the rail tracks reaching the shaft collars while they are not in operation, to prevent the accidental fall of any car or locomotive; o) Have, in stopes being worked, two access ways connected to each other; p) Have, in galleries used for haulage by means of cars on rails: 1) A clear space of at least 75 centimetres between the wall or ground support and any projecting part of the cars or the locomotive, or 2) Safety refuge bays every 30 metres, signposted and of sufficient size to shelter at least two persons; q) Leave, in galleries where a belt conveyor is installed: 1) At least 60 centimetres clear between one side of the conveyor and the wall or ground support, and 2) At least 90 centimetres clear on the side intended for worker movement; r) Provide at least 20 centimetres of clear space between the highest point of the material prism on a belt conveyor and the underside of the ground support; s) Comply, in the case of ladders, with the following safety conditions: 1) The ladder compartment shall be independent of those used in the shafts for the movement of personnel and the extraction of materials; 2) The ladder compartment shall have a guard of resistant material or wood to prevent any material that could fall down the shaft from entering the compartment; 3) Ladders shall have resting platforms at intervals of not more than 6 metres in height; 4) Ladders located in shafts that serve as an escape route shall have the dimensions necessary for a man to move freely while carrying the largest item of rescue equipment required in the underground mine; 5) The ladder shall project at least 90 centimetres above the upper platform, or shall have a handrail projecting to that same height; 6) Ladders shall maintain a minimum clear distance of 15 centimetres between the inner edge of the rung and any projection from the wall, ground support or installation; 7) Ladders shall provide continuous support to the worker's back at not more than 70 centimetres from the rung, measured transversely to the ladder, if the ladders are more than 2.50 metres in height, and 8) Cable ladders used in shaft-sinking work shall comply with the following: i. They shall not be more than 15 metres in length, and ii. They shall be fitted with stand-offs that keep them at least 10 centimetres clear of the wall or ground support faces; t) Have a maintenance programme for the installations providing for their inspection at least once a month, to ensure that they are always in a safe condition for use, and u) Keep a record of the inspections carried out on the installations.

8.4 Ventilation

8.4.1 The ventilation system of underground mines shall include, at least, the following: a) A general ventilation plan; b) The plans of the ventilation system; c) The safety requirements for ventilation workings; d) The safety conditions for fans when they are installed after having received preventive maintenance; e) The safety conditions for controlling the volume of air; f) The safety procedures for maintenance and operating work; g) The safety measures for when the concentration limits of gases such as carbon monoxide, nitrogen dioxide, sulphur dioxide or any gas or explosive material that could be generated during mining, among others, are exceeded, and h) The actions to be taken in the event of a shutdown of the ventilation system and for restoring ventilation.

8.4.2 The general ventilation plan for underground mines shall contain, at least, the following: a) The type of ventilation in the mine and in the development workings; b) The ventilation circuits; c) The location and number of ventilation shafts planned for the exploitation of the mine; d) The specifications of the fans; e) The volumes of air required at the workplaces; f) The specifications of the ducts to be used with the fans; g) The cross-section and number of air inlets and outlets in the mine, and h) The approval signature of the person responsible, designated by the employer.

8.4.3 The plans of the ventilation system shall comply with the following: a) Be up to date in accordance with the progress of the workings, or when the ventilation system is modified; b) Be approved and signed by the employer and by the person responsible for the preventive occupational safety and health services, and c) Be available at the mine office for consultation by personnel.

8.4.4 The ventilation system in underground mines shall meet, at least, the following characteristics: a) Supply inside the mine a volume of air of: 1) 1.50 cubic metres per minute per worker, and 2) 2.13 cubic metres of air per minute per horsepower of machinery powered by diesel combustion engines, located inside the mine; b) Maintain a minimum air velocity of 15.24 metres/minute, when machinery powered by diesel combustion engines is operated at any face, gallery or shaft; c) Keep the end of the ducts at a distance of less than 30 metres from the face of the excavation, when the use of ducts is necessary to achieve the required ventilation at faces, galleries or crosscuts under development; d) Have installed emergency ventilation piping with a perforated valve at the foot of the development of raises and winzes or blind shafts, allowing a continuous discharge of compressed air; e) Supervise daily that the end of the piping is less than 5 metres from the face, for which purpose the location shall be ventilated with the valve fully open for at least 10 minutes before entering the working, and f) Install fans inside the mines, ensuring that the following is complied with: 1) That the clean air entering the mine is not mixed with the vitiated air leaving it, and 2) That the sites where they are installed are kept free of combustible materials.

8.4.5 Underground mines shall have, and follow up, a programme for the inspection and maintenance of the ventilation system.

8.4.6 The programme for the inspection and maintenance of the ventilation system shall contain, at least: a) The activity to be carried out; b) The frequency; c) The dates it was carried out, and d) The person responsible for its execution.

8.4.7 The inspection and maintenance programme for the ventilation system shall provide for monthly inspections of, at least: a) The electrical substation; b) The controls and electric motor; c) The blades and fasteners; d) The transmission system; e) The lubrication system, and f) The doors and airlocks.

8.4.8 To keep a record of the inspections and maintenance of the ventilation system.

8.4.9 Underground mines shall have a procedure for reporting to the preventive occupational safety and health services any fault in the ventilation system, so that the necessary measures can be adopted to maintain safety conditions.

8.5 Fire prevention and protection

8.5.1 For fire prevention and protection in underground mines, a fire risk analysis shall be carried out that considers, at least, the following: a) The areas, activities, equipment, machinery and materials with fire risk; b) A description of the material and human resources for preventing and controlling fire; c) The need for internal or external company support and the manner in which it will be requested; d) The actions to be taken during a fire emergency; e) The actions and acts that shall be prohibited under normal conditions or during an emergency; f) The routes by which the toxic gases generated during a fire will disperse, taking into account the areas, activities, equipment, machinery and materials with fire risk; g) The dates of preparation and review of the fire risk analysis, and h) The name and signature of the person who prepared the risk analysis.

8.5.2 The fire prevention and protection analysis for underground mines shall be reviewed and, where applicable, updated at least once a year.

8.5.3 The fire prevention and protection analysis for underground mines shall indicate, at least, the following: a) The general alarm systems or mechanisms to be used redundantly in the event of fire: audible, visual, olfactory and/or wired or wireless communication, and b) The quantity and type of portable or mobile extinguishers to be placed strategically at: 1) The sites where flammable materials are stored; 2) The accesses to the mine; 3) The fixed electromechanical installations, and 4) The electrical substations and areas where the motor control centres are located.

8.5.4 Inside the mine there shall be a plan indicating the location of the fire-fighting equipment - extinguishers, hydrants and detectors - and of the communication equipment for reporting a fire.

8.5.5 The fixed fire-fighting systems used outside the underground mine shall comply, at least, with the following: a) Have water tanks with sufficient capacity to deal with a fire emergency; b) Have means for testing the system, and c) Have a water supply exclusively for fire-fighting service, independent of the water supply used for the process.

8.5.6 For fire prevention and protection in underground mines, at least the following safety measures shall be applied: a) Keep shaft collars, headframes, shaft stations or landings, yards, galleries and extraction faces free of flammable waste; b) Use non-combustible materials, non-combustible coatings or fire-resistant materials in shafts and headframes that are built; c) Install hydrants at headframes built of timber, with a minimum pressure of 7 kg/cm2, distributed in accordance with the fire prevention and protection analysis, which shall define their location for tackling any fire that might occur; d) Have self-rescuers in a quantity sufficient to guarantee the evacuation of all workers to the exit of the underground mine or to shelter in a refuge; e) Provide extinguishers appropriate to the type of fire, portable or mobile, distributed strategically, based on the fire prevention and protection analysis; f) Install the bases and supports of electric motors, transformers or any other electrical equipment, as well as the rooms where they are located, using non-combustible materials; g) Store the oils and greases used in the workshops, machine rooms and electrical substations inside the underground mine in fireproof containers or cabinets, only in quantities limited to consumption per shift; h) Accumulate grease and oil waste in closed containers, and remove them at least once a week, in accordance with the safety procedure drawn up for that purpose; i) Post signs prohibiting smoking and the use of open-flame equipment or devices in places where fuel is stored or dispensed, as well as in places supported with timber; j) Have explosion-proof electrical installations in places where lubricants and fuels are stored, and within a radius of up to 10 metres; k) Establish a fire prevention and protection procedure, when open-flame equipment or devices are used in areas supported with timber, which shall consider, at least, the following: 1) Wet the area with water before starting work; 2) Collect the slag generated by welding in metal trays; 3) Wet the area thoroughly with water after finishing work, and 4) Keep watch over the area for 30 minutes after the work has been carried out, to ensure that a fire does not start; l) Post signs prohibiting refuelling while the equipment's engine is running; m) Prohibit diesel-powered equipment from being left running if the operator is not present; n) Have a programme for the inspection and maintenance of fire-fighting systems and equipment, in accordance with the provisions of NOM-002-STPS-2010, or the standard replacing it, and o) Carry out at least one fire drill a year for each underground mine in operation.

8.5.7 In underground mines, the functionality of the general fire alarm system or mechanism shall be checked at least every six months and, where applicable, given the maintenance necessary to ensure its proper operation.

8.5.8 The record of the results of the inspections of the general fire alarm system or mechanism shall contain, at least, the following: a) The type of check carried out; b) The results obtained; c) The name of the person in charge of carrying out the inspection, and d) Any additional comments, if applicable.

8.6 Explosives

8.6.1 In underground mines, the employer shall: a) Have the permits granted by the Ministry of National Defence for the purchase, use and/or storage of explosive material, based on the provisions of the Federal Firearms and Explosives Law and its Regulations; b) Establish and apply safety procedures for the receipt, storage, transport, handling and use of explosives, to ensure a reduction in the risk of explosion in operations; c) Designate the persons responsible for issuing the corresponding authorisations for the receipt, storage, internal transport, handling and use of the explosives used, and d) Designate a person in charge of the magazine to receive, issue and oversee the handling of explosives; control their entry into, consumption at and removal from the mine; prepare a monthly report, and keep it for at least twelve months.

8.6.2 Workers who use explosives inside underground mines shall have the corresponding written authorisation for that purpose. A copy of that authorisation shall be provided to the workplace's safety and health committee and to the preventive occupational safety and health services.

8.6.3 Work with explosives in underground mines may only be started once the written authorisation is in place and the safety measures established for the activity to be carried out have been fulfilled.

8.6.4 The safety procedure for the receipt, storage, internal transport, handling and use of explosives at the mining unit shall contain, at least, the following: a) The planning of drilling and blasting; b) The control of the supply, consumption and return of explosives; c) The safety measures for the receipt and storage of explosives; d) The safety measures for the issue and internal transport of explosives; e) The safety measures for the handling and use of explosives; f) The safety measures for the loading and blasting of explosives, and g) The control and monitoring of access to blasting areas.

8.6.5 Explosives storage areas (magazines) in underground mines shall comply with the following safety conditions: a) Have drainage systems inside the magazines to keep them dry; b) Have safety signs to identify the products stored, the associated risks and the safety conditions; c) Have, at the entrance, means for discharging static electricity from personnel before they enter those areas; d) Establish the instruction that the explosives stored first shall be the first to be used; e) Set the frequency of inspections of the explosives stored, and have measures for destroying deteriorated explosives, in accordance with the manufacturer's instructions; f) Have the extinguishers and emergency control equipment necessary to rapidly combat any incipient fire and, in addition, a container of at least 200 litres of water and another of equal capacity with sand, together with a bucket and a hand shovel; g) Have a lightning-protection system, keep it in working condition and evaluate its earthing system at least once a year, in the case of magazines located on the surface or close to it; h) Prohibit the lighting of fire near the magazine and the storage of flammable or readily combustible materials inside it or in its vicinity, and i) Prohibit entry into magazines with objects liable to produce sparks or fire.

8.6.6 The safety measures for obtaining and issuing explosive material shall consider, at least, the following: a) Request in writing only the number of initiators, detonating caps and explosive agent necessary to carry out the activity; b) Include in the request, at least, the following data: 1) The name and signature of the person in charge or the authorised supervisor of the mine; 2) The name, signature and position of the worker receiving the material; 3) The dates of the request and of delivery; 4) The shift; 5) The type and quantity of material requested and delivered, and 6) The place where the explosive material is to be used; c) Have instructions for the return of unused explosives or initiators and for recording the reasons for the return; d) Have a person in charge - designated by the employer - both for the issue of materials and for the return of those not used; e) Provide that returned materials that are: 1) In good condition, shall be placed, with the applicable safety measures, in the corresponding magazines for storage, and 2) In poor condition, shall be destroyed on the basis of the procedure established for that purpose, and f) Keep a record, by shift, of the consumption of explosives.

8.6.7 The safety measures for the control of explosives shall consider, at least, the following: a) Have containers for transporting explosive material that are closed and made of spark-proof material; b) Lower explosive materials into the mine before or after personnel; c) Carry out the transport of explosive materials only with workers who have been trained and authorised for that activity; d) Transport explosives and initiators separately, from receipt to use or return; e) Transport explosives from the magazines to the working faces in separate containers and in the quantities strictly necessary for immediate use; f) Limit the quantity of explosives to 35 kilograms, if transported by hand; g) Maintain a minimum distance of 100 metres between the transport of detonating caps and initiators, or transport one of these components first and the other afterwards, keeping them separate from one another; h) Prevent initiators and detonating caps from being placed near electrical conductors, moving equipment or unsafe locations; i) Provisionally place initiators and detonating caps in authorised locations, separating them by at least a distance of 100 metres, and return them to the corresponding magazines in the same work shift when they are not used immediately, and j) Return to the magazine any materials not used in blasting.

8.6.8 The safety measures for using, loading and tamping blastholes shall consider, at least, the following: a) Observe all the safety provisions established by the manufacturers; b) Use, where applicable, initiators of the same technical characteristics and make in a single blast; c) Check each blasthole before it is loaded, using the ordinary wooden tamping rod, to make sure it is clean and to verify its direction and depth; d) Verify that blastholes have at least 60 cm of solid rock between their bottom and the point of breakthrough, when breaking with explosives is carried out in crosscuts or development workings close to breaking through; e) Clear out any debris that has accumulated inside the blastholes; f) Use only special punches made of wood, copper, aluminium or other spark-free material to pierce the detonating cap and prepare the primer charge; g) Tamp the blastholes only with the personnel necessary to do so; h) Use only wooden tamping rods to tamp the blastholes, and i) Push the detonating caps in firmly with the tamping rod and never strike them.

8.6.9 The safety measures for blasthole firing shall consider, at least, the following: a) Notify personnel in adjacent areas before carrying out blasts, and carry them out only with personnel authorised for that activity; b) Verify that all workers have left the place where the blast is to be fired; c) Post danger notices and have personnel guarding the entrances to the area where the blast is to be fired; d) Position, in a safe place, the personnel authorised by the employer to guard access to the area where the blast is to be fired, at a distance of not less than 100 metres from the face; e) Inspect the site after each blast, only by workers authorised by the employer to control ventilation and safety; f) Verify that the percentages of nitrous oxide, sulphur trioxide, carbon monoxide and oxygen are within limits that do not create risks to workers or to the workplace; g) Carry out an inspection of the area 30 minutes after the blast has been fired and when there is no smoke present; h) Post danger notices at the entrance to the face and proceed to improve the ventilation of the location, if, as a result of the inspection of the area, contents above the limit values for nitrous oxide, sulphur trioxide and carbon monoxide are found; i) Wet the blast area with water before mucking the load, to prevent dust from rising, and repeat the activity as many times as necessary; j) Prohibit workers from accessing the site where the blast was fired until the shotfirer has checked that: 1) There are no misfires and that, if any misfires are found, they are re-fired or washed out personally by the shotfirer, and 2) The walls, floor and roof are safe, and k) Prohibit blasts from being fired when their vertical projection is less than 30 metres from surface installations, unless all workers have been evacuated from the surface.

8.6.10 The safety measures for the inspection and treatment of misfired blastholes shall consider, at least, the following: a) Locate and recover the detonating caps and initiators from misfired holes after each blast, in accordance with a safety procedure that shall consider, at least: 1) The tools or implements for carrying out this activity, and 2) That it be carried out by trained and authorised personnel; b) Prohibit drilling into stemming stubs or bootlegs (leftover portions of blastholes); c) Wash and carefully inspect the stubs to check for explosives; d) Wash with water until there is enough room to place a new primer charge or to extract the explosives from the misfired holes; e) Prohibit the use of compressed air and tools that could produce sparks when extracting explosives from misfired holes, and f) Blast within a new blasthole, or else return to the magazine the explosive material (explosive or initiator) recovered from the misfired hole.

8.7 Transport of workers

8.7.1 Underground mines shall have a procedure for the transport of workers that shall consider, at least, the following: a) The means of transport to be used; b) The safe way to use and operate the means of transport for personnel; c) The communication systems to be used; d) The maximum permitted speed, where applicable, including its signposting; e) The safety procedures for the means of transport for personnel, and f) The traffic instructions.

8.7.2 Underground mines shall have operating manuals for the equipment used to transport personnel, including the safety procedures.

8.7.3 The safety procedures for the transport of personnel in underground mines shall be communicated to workers by means of signs, notices and posters located strategically in the areas designated for personnel and at the entrance to the mine, for compliance purposes.

8.7.4 The use of petrol engines shall not be permitted in equipment used to transport personnel inside underground mines.

8.7.5 Underground mines shall have, and follow up, a programme for the inspection and maintenance of the vehicles or equipment used to transport personnel, which shall contain at least the activity to be carried out, its frequency, the dates on which it was carried out, and the person responsible for its execution.

8.7.6 In underground mines, a record shall be kept of the results of the inspections and maintenance of the vehicles or equipment used.

8.7.7 Every diesel engine shall have a device for purifying exhaust gases.

8.7.8 Vehicles used for the regular transport of personnel shall have functional seats.

8.7.9 In underground mines, workers shall only be transported in vehicles designed for that purpose or in load-carrying vehicles without materials, in the latter case when they comply with the provisions of point 8.7.12 of this Standard.

8.7.10 When workers are transported in motorised vehicles in underground mines, the following safety measures shall be taken: a) Boarding and alighting stations shall be lit; b) Cars used to transport workers shall be fitted with resistant sheet-metal roofs, perimeter protection and bars or handrails to hold onto; c) Trains shall have a signal transmission system between the brakeman and the locomotive operator, and d) Operators shall be trained and instructed in the use of remote control devices for operating motorised vehicles.

8.7.11 In underground mines, the transport of persons shall be prohibited under the following conditions: a) Outside cabins and on platforms without lateral protection; b) In tipping bodies, and c) On the bodies or platforms of vehicles loaded with any type of material.

8.7.12 The transport of personnel in load-carrying vehicles shall only be permitted in situations of disaster or imminent risk, or owing to duly justified extraordinary circumstances, when those vehicles have: a) Perimeter protection on the platform that prevents the accidental fall of a worker; b) Devices allowing workers to hold on properly, and c) A platform or body without a tipping mechanism.

8.7.13 Installations and operations using rail-mounted personnel transport systems shall have, at least: a) Derailers on surface branch lines leading to warehouses, workshops or shaft collars, or connecting with the main line, when those branch lines have a downward gradient of more than 2%; b) Flags or lanterns to protect persons working or moving near the rails, and c) A signal code for the flags or lanterns, which shall be: 1) Red, to indicate danger or a full stop; 2) Amber, to indicate caution or to proceed slowly, and 3) Green, to indicate a clear path.

8.7.14 Conveyor belts for transporting workers in underground mines shall: a) Be equipped with boarding and alighting stations; b) Operate at a speed of 2 metres/second or less, and c) Have an emergency stop system along the entire route.

8.7.15 Cages used for transporting workers in underground mines shall comply with the following: a) Have a roof of resistant sheet metal; b) Be lined with sheet metal up to a height of at least 1.50 metres from the floor. The remaining part up to the roof shall be lined with metal material to prevent any material from being projected into the interior; c) Have bars or handrails for workers to hold onto; d) Have gates that can be secured during movement to prevent them from opening owing to jolts or impacts, and e) Have a minimum clear height of 2.10 metres.

8.7.16 Hoists used in underground mines shall comply, at least, with the following safety measures: a) Have, at the entrance to the control room where they are located, the corresponding signs prohibiting entry by unauthorised personnel; b) Be fitted with a depth indicator and a bell that operates on arrival at each station, which can be easily seen and heard by the operator; c) Have programmes to verify that the sheave and the linings are in good condition, in the case of friction hoists, and, when necessary, adjust the cable tension whenever the travel is adjusted or the cable or its attachment is changed; d) Have a system that can disengage the drums, which prevents the drum from being disengaged without the brakes being fully applied, and which in turn prevents the brakes from being released when the mechanism is not fully engaged; e) Have clutch engagement and disengagement controls permanently guarded to prevent accidental operation; f) Have an automatic overspeed control, for speeds above 4 metres/second, that brakes the cages or cars before they overrun the upper or lower station, and that prevents them from reaching the lower or upper station at a speed greater than 1.50 metres/second; g) Be fitted with flanges or arms for winding the cable and, in the case of conical drums, have guides or other devices to prevent the cable from slipping; h) Have the end of the cable fixed to the drum, with at least three wraps remaining, when the cage or conveyance is at the deepest point of the shaft; i) Have, on the cable-winding drums, a diameter of at least 30 times the diameter of the cable; j) Verify that the diameter and the groove of the sheave are specific to the type and diameter of the cable used, when friction hoists are used, and that the diameter is not less than 30 times the diameter of the cable; k) Verify that the brakes of hoists used for raising and lowering workers: 1) Have two independent systems acting on the drum or sheave or on their shafts, and are capable of stopping the cage, car or skip at a decelerated rate, at a speed not exceeding 5 metres/second, nor at the maximum acceleration that the hoist can produce at maximum load, and 2) Engage automatically if the motive power fails or the pressure of the braking system drops and, in the event of failure of one of the systems, the braking capacity of the other system remains available to control the cages, cars or skips, and l) Have a braking system that acts automatically on the guides in the event of breakage of the cable or its attachment, in the case of cages or cars supported by a single cable or with a single point of attachment to the cable.

8.7.17 For the use of hoists in underground mines, there shall be a safety procedure that considers, at least, the following: a) That, at the start of each shift and after each shutdown for repairs, the empty cage be moved along the shaft, to ensure that there are no obstructions or defects affecting its operation; b) That the lowering or raising of material not be carried out simultaneously with workers on the same deck of a cage; c) Instructions for acting in the event of doubt about any signal; d) Instructions for when water is present at the bottom of a shaft; e) The precautions or measures that the hoist operator shall take before leaving the controls, to prevent another unauthorised worker from starting it up; f) That inspections and tests be carried out only by workers trained and authorised by the employer, at the following intervals: 1) One day: for the visual inspection of cables, chains, connecting pieces and cable supports, and of the safety devices that prevent the free fall of conveyances or cars in the event of cable breakage; 2) One week: for the visual inspection of the external elements of the machines, the headframe, the conveyances and other elements required in those shafts; 3) Two weeks: for the visual inspection of the ground support and the walls of the shafts; 4) One month: for the detailed inspection of cables, including the detection of broken and worn wires, in the case of single-rope hoists, as well as of the motors, brakes and clutches, and for testing the safety devices that prevent conveyances or cars from falling in the event of cable breakage, and 5) Six months: for the inspection of cables by electromagnetic means, and of the parts of the hoists subject to tension, by non-destructive means; g) The record of the results of the inspections, tests and maintenance of shafts, hoists, cables, cages, cars, safety devices and other accessories; h) The procedure to follow when the drum or sheave is disengaged, in the case of double-drum hoists, and i) The frequency with which the ends of the cables shall be cut at both ends, in accordance with the inspection and testing programme.

8.8 Transport of materials

8.8.1 Underground mines shall have a safety procedure for the transport of materials that shall consider, at least, the following: a) The means of transport to be used; b) The safe way to use and operate the means of transport for materials; c) The communication systems to be used; d) The maximum permitted speed, including its signposting; e) The safety procedures for the means of transport for materials, and f) The traffic instructions.

8.8.2 Underground mines shall have operating manuals for the equipment used to transport materials, including the safety procedures.

8.8.3 The operating manuals for the equipment used to transport materials in underground mines shall be communicated by means of signs, notices or posters located strategically in the areas where personnel congregate or at the entrance to the mine, for compliance purposes.

8.8.4 The use of petrol engines shall not be permitted in equipment used to transport materials inside underground mines.

8.8.5 Every diesel engine shall have a device for purifying exhaust gases.

8.8.6 In underground mines, the safe work procedure for the transport of large-sized materials shall consider, at least, the following: a) Not allow personnel to be present along the route between the point of origin and the destination; b) Where the material transported projects beyond the vehicle, require a clear space of at least 40 cm on each side; c) Limit the speed of the equipment transporting the material according to the conditions of the route, and d) Have the operation supervised by the person in charge of the shift.

8.8.7 All wheeled, rail-mounted or tracked vehicles used to transport materials in underground mines shall comply with the following: a) Have a braking system that ensures the vehicle stops and remains stationary at maximum load and under any other operating condition; b) Have clearly visible front, rear and warning lights; c) Have an audible warning signal that activates automatically when the vehicle moves in reverse; d) Have a cabin built or reinforced in such a way that it can withstand damage caused by falling rock or materials being transported, as well as protect against impacts from the ground support; e) Have a body for transporting materials, reinforced in such a way that it withstands the load and the impact of rock or materials; f) Provide the driver with good visibility, even when the cabin is modified or equipped; g) Have a comfortable seat that reduces equipment vibration for the driver, control devices that are suitable, and access points; h) Keep the engine exhaust outlet away from the operator and, where applicable, from the air-conditioning intake, when equipment with diesel engines is used, and i) Have an ABC-type extinguisher of at least 4.5 kg.

8.8.8 At the places in underground mines where cars are coupled or uncoupled, there shall be a clear space of at least 75 cm between the cars or the locomotive and the wall or ground support.

8.8.9 Locomotives used inside underground mines shall be fitted with: a) Brakes that can be operated by the driver, regardless of whether or not other devices exist for operating them; b) A headlight with an effective range of at least 60 m; c) A comfortable seat that reduces equipment vibration for the driver, where applicable; d) Control devices arranged in such a way that the driver can operate them without diverting attention from the direction of travel; e) A portable ABC-type extinguisher of at least 4.5 kg, and f) A miner's lamp.

8.8.10 All trains used inside underground mines shall carry a luminous or reflective signal at the rear of the last car.

8.8.11 Cars not in operation shall be braked or chocked.

8.8.12 Locomotive batteries shall only be stored and replaced at charging stations fitted out for that purpose.

8.8.13 Vehicles with diesel combustion engines shall only be refuelled at the fuelling stations.

8.8.14 Vehicles powered by diesel combustion engines that show operating anomalies, additional engine noise, or, in particular, that emit noticeable smoke, throw sparks, or show water or fuel leaks, shall have their engine stopped immediately and shall be withdrawn from service for repair.

8.8.15 The tracks and traffic routes for vehicles in underground mines shall be signposted in accordance with NOM-026-STPS-2008, or the standard replacing it, indicating at least intersections, changes of direction and steep gradients.

8.8.16 For belt conveyors used to move material in underground mines, the following safety measures shall be taken: a) At the drive unit: 1) The support system for the roof or ground support of the gallery and its support blocks shall be made of non-combustible materials, with non-combustible coatings or fire-resistant materials, and 2) There shall be at least one portable 9 kg ABC-type extinguisher, or its equivalent, and b) On the conveyor belts: 1) Have an emergency stop cable running the entire length of the belts; 2) Have crossovers at points where personnel cross; 3) Have safety guards on the pulleys of the drive and tail units, and 4) Clean and maintain the belts only when they are not running.

8.8.17 Underground mines shall have, and follow up, a programme for the inspection and maintenance of the vehicles or equipment used to transport materials, which shall contain, at least, the name and description of the activity to be carried out, the frequency with which it will be carried out, the dates of execution, and the person responsible for compliance.

8.8.18 In underground mines, a record shall be kept of the results of the inspections and maintenance of the vehicles or equipment used to transport materials.

8.9 Electrical installations

8.9.1 Underground mines shall have plans of the mining operations that identify and locate, at least, the transformers, main switches, electrical controls, distribution panels, pumps, battery chargers, and telephone and communications electrical circuits.

8.9.2 The plans of the electrical installations of underground mines shall meet the following conditions: a) Be in the Spanish language; b) Specify the capacity of, at least, the transformers, battery chargers and circuit protections; c) Be available at the main substations and control rooms for consultation by workers; d) Be updated monthly and whenever there are changes or new installations in the distribution of electrical power; e) Bear the name and signature of the persons in charge of the maintenance, safety and operations areas, and f) Be kept for at least a period of twelve months.

8.9.3 The plans of the electrical installations shall include: a) The up-to-date single-line diagram, which shall include, at least: 1) The voltages of the primary and secondary windings of the transformers; 2) The type of connections in the primary and secondary windings of each transformer; 3) The impedances and rated characteristics, in kV or MVA, of the transformers; 4) The number of phases; 5) The lengths of cabling between circuit elements; 6) The conductor sizes, including those for earthing, in mm2 or MCM (circular mil x10-3); 7) The rating of circuit breakers and the rating of the protection for branch circuits, and 8) The design calculations supporting the conductor size to be used; the rating of the overload and short-circuit protection; the phase balancing; the capacity of the circuits, and the characteristics of the electrical equipment to be used in the mine's electrical installations; b) The general load schedule; c) The emergency generating sets; d) The metering points; e) The load centres or panels; f) The transfer switches, and g) The earth fault detection devices or systems.

8.9.4 Underground mines shall have safety procedures for: a) The fitting of safety tags and padlocks; b) The installation of electrical conductors and equipment; c) The splicing or connection of cables; d) The discharge of residual voltages from installed equipment; e) The inspection of electrical installations, including verification of the good condition of the branch circuit protections; f) The verification of electrical continuity and measurement of the resistance of the earthing system, and g) The measurement of the insulation resistance of cables.

8.9.5 The safety procedures shall include, at least, the following: a) Instructions for applying safety measures; b) The sequence of actions that personnel shall carry out for the activity; c) The type of tools, instruments or equipment to be used; d) The personal protective equipment that, where applicable, the worker shall wear, and e) Instructions for acting in the event of an emergency.

8.9.6 Underground mines shall have an annual programme for the inspection and maintenance of the electrical installations, based on the provisions of NOM-029-STPS-2011, or the standard replacing it.

8.9.7 The annual programme for the inspection and maintenance of the electrical installations of underground mines shall include, at least, the following: a) The activity to be carried out as a result of the inspection; b) The equipment subject to inspection or maintenance; c) The code or identification number of the equipment subject to inspection or maintenance, where applicable; d) The procedure for fitting safety tags and safety padlocks; e) The safety measures to be adopted; f) The frequency of the activity; g) The start and completion dates of the activity, and h) The person responsible for the activity.

8.9.8 The record of the results of the maintenance programmes for the electrical installations of underground mines shall contain, at least, the following information: a) The name of the equipment, device or connection subject to maintenance; b) The date on which the activity was scheduled; c) The date on which the activity was carried out; d) The type of activity carried out; e) The results of the activity carried out; f) The code or identification number of the equipment, device or connection subject to maintenance, where applicable, and g) The name of the person responsible for the activity.

8.9.9 Electrical installations inside underground mines shall be approved by an electrical or electromechanical engineer.

8.9.10 Only personnel trained and authorised by the employer shall carry out installation, maintenance or repair work on electrical installations.

8.9.11 The cables of the signalling and telephone systems shall be: a) Installed independently and separately from the cables of the power and lighting systems; b) Protected against any contact with other conduits and apparatus, and c) Protected against any induction effect.

8.9.12 Electrical installations inside underground mines shall have an earthing system for discharging currents generated by insulation faults or other types of electrical faults, and by static electricity generated in the processes, to prevent electrical hazards to workers and equipment, as well as fire or explosion hazards.

8.9.13 In underground mines, the operation of the earthing system shall be evaluated at least once a year, and the results of the earthing system's resistance shall be recorded, in accordance with NOM-022-STPS-2008, or those that replace it.

8.9.14 Electrical equipment installed in underground mines shall have protection against overload, short circuit, earth fault and phase loss.

8.9.15 Protection against overload, short circuit, earth fault and phase loss of electrical equipment installed in underground mines shall be indicated in the calculation report and in the single-line diagram.

8.9.16 Electrical equipment used in underground mines shall comply with the following characteristics: a) Have overcurrent and short-circuit protection devices, in accordance with the voltages of the supply lines of each branch circuit where they are installed; b) Bear identification on the equipment itself, painted or by means of self-adhesive labels, indicating its electrical characteristics and, at least, the operating voltage, as well as the circuit or equipment it supplies; c) Have physical protection preventing unauthorised workers from coming into contact with the surface and connection terminals of the transformers; d) Have devices that interrupt the power supply to the entire electrical installation outside the mine, and devices that interrupt the power supply for each of the branch circuits; e) Have a power supply lead with a diameter matching the electrical cable, for heavy-duty use, and waterproof and dust-proof, and f) Have supply by means of cables with electrical terminals: 1) In conditions that allow their design characteristics to be preserved (for example, not broken, loose, deformed, or slack, among others), and 2) Packed and completely secured to the base of the equipment by means of fasteners.

8.9.17 Mobile equipment driven by electric motors that is remotely controlled shall have the following: a) Emergency stop devices: 1) With mechanical interlock; 2) Located next to the equipment itself, and 3) Within reach of workers, and b) Safety switches: 1) That are signposted; 2) That are located within reach of workers who work next to this equipment, and 3) That prevent the motor from starting until the switch has been closed manually.

8.9.18 Electric motors installed inside underground mines shall comply with the following: a) Have electrical terminals on the electrical cable connections matching the cable diameter; b) Have a device to monitor the continuity of the electrical cable, in the motor's connection box; c) Have cooling systems; d) Have protection in the motor connection boxes against moisture, falling material and the operational movements of the machines; e) Be located in the same area as the starting and stopping circuit or circuits, and f) Have the surrounding area clean and tidy.

8.9.19 Portable electrical equipment used with supply potentials of 440 volts or higher shall have automatic power cut-off systems in the event of an earth fault.

8.9.20 Electrical transformer substations installed inside underground mines shall comply with the following: a) Be at distances greater than 50 metres from any quantity of explosives for immediate use; b) Have at least one 9 kg type ABC extinguisher or its equivalent; c) Be in ventilated locations; d) Have overcurrent or other fault protection devices on each low-voltage branch circuit; e) Be connected to an earthing system; f) Have protective railings to prevent and control the passage of personnel, equipment or materials; g) Be built of non-combustible materials, with non-combustible coatings or fire-resistant materials, and be equipped with suitable fire-extinguishing elements, and h) Have safety signs, based on the provisions of NOM-026-STPS-2008, or those that replace it.

8.9.21 Mobile or portable machinery driven by electric power shall comply with the following: a) Supply cables: 1) Be of the flexible type; 2) Be heavy-duty; 3) Be firmly secured to the machinery to prevent their terminals from being damaged or accidentally disconnected; 4) Be positioned so that they are not mechanically stretched; 5) Be placed on supports to prevent them from getting wet, and 6) Be kept on supports designed for that purpose in the case of additional extensions; b) Electrical controls supplying machinery with 440 volts or more shall be installed on metal frames located in the galleries of the working faces; c) Junction boxes shall be firmly suspended and not exposed to impacts and water, and d) Supply outlets of any voltage level shall not be located in the hoisting towers, in stations or windows, nor along the shafts.

8.9.22 Cables used in underground mines shall comply with the following: a) Be heavy-duty; b) Have flame-retardant or self-extinguishing insulation; c) Comply with the electrical characteristics indicated on the drawings and in the calculation report attached to the single-line diagrams; d) Be of the flexible type and of the gauge required to prevent overheating due to electrical load, in the case of electrical cables used to connect portable electrical equipment; e) Be protected from moisture and kept away from contact with water pipework; f) Be separated from compressed-air pipes and communication lines; g) Be installed in such a way that they do not suffer mechanical damage; h) Be placed on supporting means and on the wall opposite the location of the water and air networks. Where this is not feasible, they shall be located on the roof or in a place higher than the networks mentioned above; i) Be electrically connected to the earthing system, or to a system of earthing rods at each electrified level of the mine; j) Be supported in such a way that they are not on the floor of the underground mine. Those installed in inclined shafts or boreholes whose conductors or sheaths cannot support their own weight shall have supports capable of withstanding their weight at distances of no more than 10 metres, and k) Avoid their use to supply electrical equipment when they are bare.

8.9.23 Areas where transformers or substations are located in underground mines shall have safety signs complying with the provisions of NOM-026-STPS-2008, or those that replace it, and indicating, at least, the following: a) That they are in operation and/or energised; b) The mandatory use of personal protective equipment, where applicable, and c) The prohibition of access to unauthorised persons.

8.9.24 In underground mines, there shall be a specific place or room for battery charging that is separate from the transport routes.

8.9.25 Rooms intended for battery charging in underground mines shall comply with the following safety conditions: a) Have walls and columns of non-combustible materials, with non-combustible coatings or fire-resistant materials; b) Have the installation of any electrical element in the upper part of the charging room prohibited; c) Be outside the influence of any mining work; d) Be equipped with a first-aid kit, taking into account possible burns or accidents caused by battery electrolyte; e) Have emergency showers and eyewash stations; f) Have, in an accessible location, the means necessary to contain and chemically neutralise electrolyte leaks or spills; g) Have natural or forced ventilation, including their upper parts (hoods); h) Have power supply switches for all circuits installed in the room, for use when ventilation is interrupted, and i) Have signage prohibiting smoking or bringing in lighters, matches or ignition tools.

8.9.26 Persons in charge of operating mobile equipment or portable electrical machines or similar equipment shall adopt, at least, the following safety measures: a) De-energise and/or disconnect the equipment every time they leave it; b) Inform the health and safety committee and the employer of any fault detected in the equipment; c) Post notices or warning signs indicating that the equipment has faults or defects, to prevent its use, where applicable, and d) Not operate or use equipment fitted with a lockout and warning system unless expressly authorised, following verification of its condition and confirmation that such action does not involve a risk to the safety of persons, equipment or facilities.

8.9.27 It shall be prohibited to work with live electrical circuits in places inside underground mines where explosives, or flammable or combustible substances, are used or handled.

8.10 Machinery and equipment

8.10.1 The operation and maintenance of machinery and equipment used in underground mines shall be carried out only by personnel authorised and trained by the employer.

8.10.2 An updated list shall be kept of the machinery and equipment used inside the mine for exploration, exploitation, extraction and the transport of workers and materials, indicating for each item, at least, the following: a) The asset number or identification code assigned to it; b) A general description of its use; c) The type of fuel or energy used, and d) Its usual location.

8.10.3 For the operation and maintenance of machinery and equipment in underground mines, work procedures shall be in place containing the applicable safety measures and prohibitions, in accordance with the corresponding risk analysis.

8.10.4 Safety procedures for carrying out maintenance activities on machinery and equipment used in underground mines shall consider, at least, the following: a) The safety measures to be adopted in the area where maintenance is carried out, such as cordoning off and signposting, among others; b) The safety measures to be applied to the machinery or equipment during maintenance, such as power cut-off, and the fitting of safety padlocks and tags, among others; c) The equipment, tools and substances to be used; d) The personal protective equipment that the worker carrying out the maintenance shall wear, and e) The authorisations that the worker shall obtain before carrying out the activity, where applicable.

8.10.5 In underground mines, there shall be a maintenance programme for the machinery and equipment that considers, at least: a) The asset number or identification assigned to the machinery or equipment; b) The scheduled dates for carrying out maintenance; c) The maintenance routines, including verification of safety devices, and d) The signature of the person responsible for scheduling the activity.

8.10.6 The record of the results of the maintenance programmes shall contain, at least, the following information: a) The date on which the activity is carried out; b) The type of activity carried out; c) The results of the activity carried out, and d) The name of the worker who carried out the activity.

8.10.7 Pulleys, gears, transmission systems, rotating shafts and other moving parts of machines and mechanical equipment used in underground mines shall have fixed guards or protective covers to prevent injury to personnel.

8.10.8 Guards and protective and safety devices for machinery and equipment, including emergency stop devices, shall be kept in safe operating condition.

8.10.9 When workers need to access certain areas or confined spaces within a machine or equipment with moving parts, to carry out activities related to its operation or maintenance, an energy lockout or isolation and signposting procedure developed for that purpose shall be applied, ensuring that the machine or equipment cannot be started inadvertently until the worker who locked out the machine or equipment removes the protection.

8.11 Vehicles

8.11.1 The operation of vehicles used in underground mines shall be carried out only by personnel trained and authorised by the employer.

8.11.2 In underground mines, there shall be an updated list of the vehicles used, indicating for each one, at least, the following: a) The asset number or identification code assigned to it; b) A general description of its use, and c) Its usual location.

8.11.3 There shall be an inspection and maintenance programme for vehicles used inside underground mines that considers, at least, the following: a) The asset number or identification assigned to it; b) The scheduled dates for carrying out the inspection; c) The maintenance routines, including verification of safety devices, and d) The characteristics of the results of the activity routines.

8.11.4 The record of the results of the maintenance programmes shall contain, at least, the following information: a) The date on which the activity was carried out; b) The type of activity carried out; c) The results of the activity carried out, and d) The name of the worker who carried out the activity.

8.11.5 Trains, locomotives, excavating machines and cars or gondolas used in underground mines shall comply with the following safety conditions: a) Locomotives shall be fitted with a headlamp with an effective range of at least 60 metres; b) Trains hauled by locomotives shall have a luminous or reflective signal at the rear of the last car or gondola; c) Cars or gondolas out of operation shall be braked and locked; d) Trolley-type locomotives shall have the following safety measures: 1) Overvoltage protection on the trolley contact lines; 2) Switches or circuit breakers on all supply branches for the different branches of the supply lines; 3) A minimum trolley line height of 2.15 metres above the rail, or above the floor where there is no rail, or protection to prevent contact with workers; 4) A clearance of at least 15 centimetres between the trolley lines and the roof, walls or projections of supports or timbering; 5) Trolley lines mounted on non-combustible insulators, firmly secured; 6) Insulating protection to prevent the trolley lines from making contact with equipment at road crossings, hoppers and chutes, work areas and canteens, and 7) Insulating protection for any metal object located above the trolley lines, except for the trolley's own supports; e) Trains and excavating machines mounted on rails or other types of guides shall not operate or move unless the good condition of the track or guide has been verified, and f) Locomotive batteries shall be stored and replaced only at charging stations fitted out for this purpose, which shall be properly ventilated to prevent the accumulation of hydrogen.

8.11.6 Vehicles powered by engines in underground mines shall comply with the following safety conditions: a) Have compression-ignition diesel engines, designed with a catalytic converter and to run only on diesel fuel; b) Be equipped with a device for cooling the exhaust gases and with spark control from the exhaust pipe, where they are not fitted with a catalytic converter; c) Use only diesel fuel with a sulphur content of less than 1.5%; d) Be withdrawn from service when they show anomalies in running, additional engine noise, noticeable smoke emissions, water or fuel leaks, or emit sparks; e) Be subject to evaluations of exhaust gas concentrations in the places where they operate, at least monthly; where there is evidence of a malfunction, or after every major maintenance or tune-up, at a maximum distance of 30 centimetres from the exhaust pipe outlet, such that the gas concentration does not exceed the following limits by volume: 1) Carbon monoxide: 0.25%; 2) Nitrogen dioxide: 0.10%; 3) Sulphur dioxide: 0.10%, and 4) Aldehydes: 0.001%, and f) Be refuelled, outside the mine, only at stations located at a distance greater than 50 metres from the accesses.

8.11.7 It shall be prohibited for vehicles powered by diesel combustion engines to be left running when the operator leaves them unattended.

8.11.8 Diesel refuelling stations for engines located inside the mine shall comply with the following: a) Be equipped with supply systems that prevent fuel spillage, and with a collection system; b) Be surrounded by a collection bund of at least 1.5 times the volume of the container, so that, in the event of a fuel spill, it is prevented from spreading to other areas; c) Not exceed, in the quantity of fuel stored, the amount consumed inside the mine over 72 hours, and d) Introduce fuel only in metal drums, sealed tanker wagons, or pipelines exclusively for this purpose, which, upon completion of unloading, shall invariably be left empty.

8.11.9 The area inside the underground mine where vehicles powered by diesel combustion engines undergo preventive maintenance shall: a) Have two independent exits; b) Be built of non-combustible materials, with non-combustible coatings or fire-resistant materials, and c) Be properly ventilated.

8.12 Floors and roadways

8.12.1 In underground mines, floors and roadways shall comply with the following safety conditions: a) The floors of areas where workers or vehicles travel shall remain free of material waste and other objects that could cause an accident, and b) Roadways shall: 1) Have a width at least 60 centimetres greater than the widest vehicle travelling on them; 2) Have a height at least 20 centimetres greater than the tallest vehicle travelling on them, but never less than 2 metres; 3) Have adequate widened sections for vehicles to cross and overtake, signposted so that they are visible from both directions; 4) Have drainage ditches in places where water may pool; 5) Have a gradient not exceeding 27.5% on ramps, and 6) Not have gradients exceeding 5% where the ramp ends at a discharge point such as a shaft or hopper.

8.13 Flooding

8.13.1 The hydrological study of underground mines referred to in item 8.1.1, subparagraph c), of this Standard, shall contain, at least, the following: a) The plans of the extraction operations, with the location of aquifers near the site of the mining operation and of surface water bodies, such as rivers or lakes, among others; b) The location of old or abandoned workings near the area to be mined, and c) The determination of the minimum permitted proximity limits to old or abandoned workings that could be flooded, for mining purposes, based on the rock mechanics study and on the topography and geology of the site.

8.13.2 The hydrological study of underground mines shall be updated when: a) The extraction processes are modified; b) New areas to be mined towards areas not considered in the study are assessed, and c) The results of the reviews indicate unusually high frequencies and quantities of water seepage into the mine.

8.13.3 According to the results of the hydrological study of underground mines, the risk prevention and control measures shall be determined, where applicable, which shall contain, at least, the following: a) The characteristics of the barriers or protective pillars between the working area and the old workings or body of water; b) The operating procedures for extraction advance and for maintaining the barrier or protective pillar; c) Exploratory drilling near faults and, in general, in geological formations that, due to their characteristics or based on experience from upper levels of the mine, could contain stored water or connect to an aquifer or flooded mine; d) The characteristics of the pumping system, and e) The emergency response plan, in accordance with the provisions of Chapter 13 of this Standard.

8.13.4 The hazardous locations shown on the plans identifying areas of water accumulation near the working areas shall be made known to workers.

8.13.5 Where there are old workings in the area that could be flooded, as well as aquifers near the mine's working area, the following safety measures shall be carried out (See Figure 2): Figure 2 Drilling in Areas at Risk of Flooding a) Drill at the heading of the working using a borehole with a length of at least 30 metres, which shall be located at the centre of it; b) Always maintain a protective barrier of at least 5 metres. The maximum length of the drilling is not restrictive, and c) Carry out, at each corner of the working, boreholes at 30º to the walls with a minimum length of 1.5 times the length of the drilling for blasting.

8.13.6 The record of exploratory horizontal drilling work shall contain, at least, the following: a) The drilling pattern; b) The lengths of the boreholes; c) The diameter of the boreholes; d) The length of the protective barrier left after the advance of the working; e) The presence of water in the boreholes, where applicable; f) The shifts in which the boreholes were drilled; g) The dates of execution, and h) The names of the worker and supervisor.

8.13.7 To control the inflow of water inside the mine, pumping systems available at all times shall be provided, shown on a plan that contains, at least: a) The location of the pumps; b) The diameters of the pipes; c) The types and capacities of the pumps, and d) The discharge points of the pumped water.

8.13.8 The entrances to mine workings shall be protected with collars positioned out of reach of surface water floods.

8.14 Refuge chambers

8.14.1 Inside underground mines, fixed or mobile refuge chambers shall be installed and available for use.

8.14.2 The size of the refuge chambers, their number and location inside underground mines shall be determined based on: a) The analysis carried out annually to identify hazards and control risks; b) The likelihood of fires or collapses occurring, and c) The advance of the working faces.

8.14.3 For the installation of refuge chambers, at least the following shall be considered: a) That the minimum and maximum distance from the refuge chambers to the workplaces is based on the risk analysis for hazard identification and risk control, and b) That they are located at a distance of more than 60 metres from the explosives magazines.

8.14.4 Fixed or mobile refuge chambers inside mines shall: a) Be built of fire-resistant materials; b) Have an area per person inside the refuge chamber of at least 0.66 m 2; c) Have a volume per person inside the refuge chamber of at least 1.2 m 3; d) Ensure that an oxygen concentration in the range of 18 to 21% exists inside it, and that gases from outside do not penetrate the refuge chamber; e) Withstand a ground pressure of at least 1.05 kg/cm 2, in the case of mobile refuge chambers, and f) Have hermetically sealed doors.

8.14.5 Refuge chambers shall be equipped with the essential items referred to in item 8.14.6, in such a way as to ensure the survival of workers inside them for a period of at least 96 hours.

8.14.6 Refuge chambers shall be equipped, as a minimum, with the following items: a) Self-rescuers in a number equal to the capacity of the refuge chamber; b) Non-perishable food meeting basic nutritional requirements (calories); c) Drinking water, which shall be renewed frequently; d) Oxygen tanks, piped compressed air and/or fresh-air ventilation from the surface; e) Equipment or elements for scrubbing carbon dioxide; f) Communication equipment with the surface or adjoining areas; g) First-aid kit; h) No-smoking signage; i) A latrine; j) Its own lighting; k) Carbon monoxide and oxygen detectors, and l) Recreational material for use during confinement.

8.14.7 For the use of refuge chambers inside underground mines, instructions, manuals or procedures shall be available: a) Within reach of workers; b) Prepared in accordance with the manufacturer's instructions or those of the occupational health and safety prevention services; c) With instructions for behaviour inside the refuge chamber and the rule for appointing a person in charge, and d) With a copy of the emergency procedure in the event of fire.

8.14.8 The location of refuge chambers shall be indicated on the plans, which shall be made available to workers, and inside the mines by means of the corresponding signage.

8.14.9 There shall be a programme for inspecting the good condition of the refuge chambers and confirming that they have the items necessary for their use. This inspection programme shall consider, at least, the activity to be carried out, the dates of execution, the person responsible for carrying it out, and the outcome of the inspection.

8.14.10 Inspections of refuge chambers shall be carried out, at least every three months, by whoever is designated by the employer and by the health and safety committee.

8.14.11 Underground mines shall keep a record of the inspections carried out on refuge chambers.

9.1 Studies and plans

9.1.1 Before carrying out work in open-pit mines, at least the following studies shall be available: a) Geotechnical: rock mechanics or soil mechanics studies; b) Geological studies, to locate faults and rock types, and c) Hydrological studies, to assess flood risks, together with the procedures for their control.

9.1.2 Geotechnical, geological and hydrological studies shall be updated when the original conditions taken into account in their preparation are modified or altered.

9.1.3 Geotechnical, geological and hydrological studies shall be kept for the operational life of the mine.

9.1.4 In open-pit mines, plans of the mining operations shall be available, meeting the following characteristics: a) Be updated in accordance with the progress of the works; b) Be approved and signed by the employer, as well as by the person in charge of the occupational health and safety prevention services, and c) Be available at the mine office for consultation by personnel.

9.1.5 Mining operation plans shall contain, as a minimum, the following: a) Topographic information indicating roads, areas where ore and waste rock are broken, as well as dumping areas; b) The surface profile, including subsidence; c) Crosscuts, galleries, exploration and working faces, stopes, backfill and other pre-existing underground mine workings; d) The location of pumping stations, where applicable; e) The electrical installation showing the single-line diagram; load schedules, as well as the voltage of the wiring and electrical equipment, and f) The location of fire extinguishers, first-aid stations and personal protective equipment for emergencies.

9.2 Excavations

9.2.1 In open-pit mines, excavation and ground stabilisation activities, as well as inspection activities, shall be carried out only with personnel trained and authorised by the employer.

9.2.2 In open-pit mines, safety procedures shall be in place for carrying out excavation and ground stabilisation, to prevent risks to workers, based on the studies referred to in item 9.1.1 of this Standard.

9.2.3 The safety procedure for carrying out excavation in open-pit mines shall consider, at least, the following: a) Information from the geotechnical, geological and hydrological studies; b) The requirement that only authorised personnel carry out this activity; c) The machinery and equipment to be used; d) The physical properties of the rock materials to be excavated, such as hardness, stability or fracturing; the materials used for backfill, where applicable, as well as the presence of moisture and clay, among others, and e) The safety measures to prevent excavations from connecting with a water source or saturated material, in accordance with the hydrological study.

9.2.4 In open-pit mines, safety procedures for carrying out excavations and ground stabilisation shall be available for consultation by any worker participating in the activity.

9.2.5 To carry out excavation and ground stabilisation activities in open-pit mines, the following safety measures shall be observed: a) Place safety signs or notices at abandoned surface excavations, waste dumps or spoil heaps, as well as in areas that pose a risk to workers, and b) Carry out an inspection, before resuming work, in those workings whose operation has been suspended for some time, to verify that there are no hazardous conditions in: 1) Stabilisation; 2) Drainage systems, where applicable, and 3) Traffic surfaces.

9.2.6 The operation of machinery used for excavation shall be carried out based on the operating manual or the manufacturer's instructions and in accordance with the recommendations derived from the geotechnical study.

9.2.7 Machinery operating manuals or instructions shall be in Spanish and available to workers who carry out or take part in these activities.

9.2.8 In excavation activities, machinery shall comply with the following safety conditions: a) Cabin windows shall be fitted with safety glass or similar material in good condition and shall be kept clean; b) The cabins of all excavators shall be equipped in such a way that the operator can see the working face at all times; c) There shall be a means of communication, as applicable, between the machine operator and the operation control booth, or between the excavator operator and the operator of the truck being loaded; d) All starting and control levers shall be immediately placed by the operator in the off position, in the event of an unforeseen interruption of the electrical power supply, and e) Workers shall be prohibited from getting on or off an excavator while it is in operation.

9.2.9 To carry out excavation activities using bucket excavators, at least the following safety measures shall be adopted: a) Follow the manufacturer's instructions for carrying out the excavator's travel movements; b) Adopt additional safety measures when the excavator moves on a slope, to prevent the excavator from sliding; c) Carry out the excavator's movements with the assistance of a worker who assists the operator, who shall remain in view of the operator at all times; d) Keep excavators on a firm, level base whose slope does not exceed the maximum specified in accordance with the rock mechanics study; e) Maintain a distance of not less than 2 metres between the edge of the bench, waste dump or any transport vehicle and the counterweight of the excavator, or in accordance with the manufacturer's recommendations; f) Position the excavator cabin in such a way as to allow visibility for the operator during operation; g) Establish safety distances when two or more types of excavator are operating at the same time in the same work area; h) Ensure that there is a clear path at all times for the excavator to leave the mine's working face, and i) Verify that excavators are able to stop and move immediately to a safe place when any hazardous situation is observed and, in particular, when there is a likelihood of rockfalls from the working face.

9.2.10 To carry out material loading and unloading activities, at least the following safety measures shall be adopted: a) Use vehicles specifically designed and, where applicable, approved for loading materials; b) Verify that, during loading activities, the following is complied with: 1) The truck operator does not get on or off the cab; 2) The loaded bucket of any shovel or loader does not manoeuvre over the cab of the operator of a truck or motor vehicle; 3) Workers keep away from the clear space between the loading unit and the loading face, and from the area swept by the machine's bucket during the loading operation; 4) Rocks of large dimensions that cannot be handled safely are broken before loading, and 5) Material is loaded in such a way as to minimise spillage during loading movements, and c) Verify that, during unloading operations, the following is complied with: 1) Loads are tipped before reaching the edge of the dump, when the ground cannot support the weight of a vehicle. To tip a load, an effective stop block or berm shall be installed, with a height equal to half the height of the tyre of the largest truck used, or a worker shall be positioned in a safe place with the required personal protective equipment to assist the driver into a safe unloading position; 2) Guides or safety signs are placed so that the driver limits their approach to the stable dumping area when there are cracks in the ground indicating instability, and 3) Artificial lighting is provided in the unloading area when dumping takes place in poor visibility or at night.

9.3 Extraction

9.3.1 The extraction methods used shall consider, at least, the following: a) The stability of walls, faces and slopes; b) The type of machinery and equipment to be used; c) The safety conditions for the movement of persons or vehicles, and d) The stability of the area before work or movement through the place is authorised.

9.3.2 Extraction shall be carried out until ground stabilisation work has been completed.

9.3.3 For extraction in open-pit mines, at least the following shall be complied with: a) Mark and delimit the area in such a way as to prohibit entry by unauthorised personnel; b) Carry out ground stabilisation from a safe location; c) Maintain the vertical height of a bench: 1) 3 metres on manual excavation working benches for unconsolidated or loose material; 2) 8 metres maximum when working manually, and 3) Based on the geotechnical study, when working mechanically, taking into account the nature of the ground and the type of machinery used. This study shall establish the specific safety conditions and procedures for the case in question; d) Prevent a worker from carrying out activities or moving between the machinery or equipment and the wall or face of a bench; e) Carry out drilling for the benches from their upper part, when mines have a face whose vertical height exceeds 3 metres and explosives are being used; f) Carry out excavations at working faces with stable slopes with an inclination no greater than that recommended by the geotechnical study; g) Limit the maximum height of the working face of a sand mine so that it does not exceed the vertical reach of the excavating equipment working on that face. Where the total depth of an excavation in a sand mine exceeds the vertical reach of the excavating equipment used, the mine shall be worked in benches; h) Reduce slopes to the material's angle of repose. Where work is interrupted on any of the benches of a sand mine for a period longer than one shift, the width of the benches shall be such as to allow this operation, and i) Each bench shall have its own loading facility and be wide enough to carry out activities under safe working conditions.

9.3.4 In the extraction of open-pit mines, the following shall be prohibited: a) Carrying out blasts in underground mines where their vertical projection is less than 30 metres from surface facilities or from the open-pit mine, and precautions have not been taken to evacuate all workers from the surface; b) Carrying out blasts in the open-pit mine where their vertical projection is less than 60 metres from an underground mine and personnel have not been evacuated from the affected area in the underground mine, and c) The combination of vertical drilling at the top and horizontal drilling at the toe, especially for carrying out successive blasts.

9.4 Installations

9.4.1 The structures of buildings and installations at an open-pit mine shall preferably be built of non-combustible materials, with non-combustible coatings or fire-resistant materials, and shall be kept in good condition, so that they do not pose risks to workers.

9.4.2 In the workings of open-pit mines, the following safety conditions shall be observed: a) Protect shafts and workings where a person could fall into a void, with structural elements such as mesh, grilles, walls or plugs, among others, where nearby underground mines exist. Where doors are used at shafts, they shall be fitted with locks to prevent them from opening unintentionally; b) Signpost and protect cavities or subsidence that form on the surface, to prevent workers, materials and/or vehicles from falling; c) Provide safe means of access to the places where workers have to move around or carry out their activities; d) Install emergency lamps that operate automatically or manually on electrically powered equipment, for use in the event of a failure in the electrical power supply, and e) Establish and signpost the maximum vehicle travel speed.

9.5 Fire prevention and protection

9.5.1 For fire prevention and protection in open-pit mines, the provisions of NOM-002-STPS-2010, or those that replace it, shall be complied with.

9.5.2 In addition to the provisions of item 9.5.1 of this Standard, fire extinguishers of the capacity and fire type that may occur shall be provided, strategically distributed at: a) Sites where flammable materials are stored; b) Electrical substations and areas where motor control centres are located; c) Machine rooms, boiler rooms, parking areas for locomotives or vehicles, workshops and warehouses, and d) Major mobile machinery or equipment.

9.6 Explosives

9.6.1 In open-pit mines, the permits granted by the Ministry of National Defence for the purchase, consumption and/or storage of explosive material shall be held, on the basis of the provisions of the Federal Firearms and Explosives Act and its Regulations.

9.6.2 For the receipt, storage, transport, handling and use of explosives in open-pit mines, safety procedures shall be in place.

9.6.3 Personnel designated by the employer shall issue the corresponding authorisations for controlling the receipt, storage, internal transport, handling and use of explosives.

9.6.4 Control of the entry, exit and consumption of explosives shall be carried out by a person in charge of the magazine, designated by the employer.

9.6.5 There shall be a control system for the inventories of explosives used.

9.6.6 Workers who use explosives in open-pit mines shall hold the corresponding written authorisation for that purpose, a copy of which shall be provided to the workplace's health and safety committee and another to the occupational health and safety prevention services.

9.6.7 Work with explosives in open-pit mines may only be started when the written authorisation is held, and the safety measures established for the activity to be carried out have been met.

9.6.8 The safety procedure for the receipt, storage, internal transport, handling and use of explosives at the mining unit shall contain, at least, the following: a) The planning of drilling and blasting; b) Control of the supply, consumption and return of explosives for the blast-loading process; c) Safety measures for the receipt and storage of explosives; d) Safety measures for the delivery and internal transport of explosives; e) Safety measures for the handling and use of explosives; f) Safety measures for the loading and blasting of explosives, and g) The control and monitoring of access to blasting areas.

9.6.9 Explosives storage areas (magazines) in open-pit mines shall comply with the following safety conditions: a) Have drainage systems to keep them dry; b) Have safety signs to identify the products stored and/or the safety conditions to be met; c) Have, at the entrance, means for discharging static electricity from personnel before entering such areas; d) Establish a first-in, first-out system for items entering the magazine; e) Set the frequency of inspections of the explosives stored, as well as provide for the destruction of deteriorated explosives, in accordance with the manufacturer's instructions; f) Have the fire extinguishers and emergency control means necessary to quickly fight any incipient fire, with an open container of 200 litres capacity with water and another of equal capacity with sand, with a bucket and a hand shovel; g) Have lightning conductor systems in working condition and evaluate their earthing system at least once a year; h) Prohibit the storage of flammable or easily combustible material inside or near the magazines, and i) Prohibit entry into the magazines with objects liable to produce sparks or fire.

9.6.10 For the delivery and receipt of explosive material, workers carrying out activities with this type of material shall: a) Request in writing only the number of initiators and explosive agents necessary to carry out the activity; b) Include in the request, at least, the following details: 1) The name and signature of the person in charge or of the mine's authorised supervisor; 2) The name, signature and position of the worker receiving the material; 3) The dates of request and delivery; 4) The shift; 5) The type and quantity of material requested and delivered, and 6) The place where the explosive material is to be used; c) Have instructions for returning unused explosives or initiators and recording the reasons for the return; d) Have a person in charge - designated by the employer - both for the delivery of materials and for the return of unused ones; e) Separate returned materials in good condition, with the applicable safety measures, from those returned in poor condition, which shall be destroyed in accordance with the procedure established for that purpose, and f) Keep a shift record of explosives consumption.

9.6.11 Safety measures for the control of explosives shall, at least, cover the following: a) Have containers for transporting explosive material that are closed and made of spark-proof material; b) Carry out the transport of explosive materials only with workers who have been trained and authorised for that activity; c) Carry out the transport of explosives and initiators separately, from receipt through to use or return; d) Carry out the transport of explosives from the magazines to the working faces in separate containers and in the quantities strictly necessary for immediate use; e) Maintain a minimum distance of 100 metres between the transport of explosives and initiators, or transport one of these components first and the other afterwards, and f) Return to the magazine any explosive materials not used in blasting.

9.6.12 For the transport of explosives in vehicles, the following safety measures shall be complied with: a) Vehicles shall be fitted with: 1) Insulated bodywork, with no exposed metal parts that could cause sparks in the load space; 2) Extinguishers of at least 9 kg, or their equivalent, of the ABC type; 3) Wheel chocks, and 4) A battery with a switch allowing it to be isolated, where powered by an internal combustion engine; b) Vehicles shall be marked to indicate that they are transporting explosives or initiators; c) Vehicles carrying explosives, when parked, shall: 1) Have the handbrake applied; 2) Have the engine switched off; 3) Be kept immobilised by means of wheel chocks, and 4) Be kept under watch; d) Vehicles shall be emptied and cleaned beforehand before being taken to a repair workshop; e) Trailers used for the transport of explosives shall be fitted with effective brakes and coupled to the towing vehicle by means of a suitably designed rigid tow bar, and with safety chain couplings, and f) The operation of vehicles transporting explosives or initiators shall be carried out only by personnel authorised for that purpose.

9.6.13 For the use and loading of boreholes, at least the following safety measures shall be complied with: a) Observe all safety provisions established by manufacturers on the matter; b) Establish, in the safety procedure on the use and loading of boreholes, a prohibition on carrying out this activity when an electrical storm is approaching; c) Check each borehole before loading, and d) Use only special punches made of wood, copper, aluminium or other spark-free material to prepare the primer.

9.6.14 To carry out blasting operations, at least the following safety measures shall be considered: a) Notify mine personnel before carrying out blasting operations; b) Post hazard warnings and have personnel available to guard access to the area where blasting is to take place; c) Position, in a safe location, personnel authorised by the employer to guard access to the area where the blast is to be carried out, at a distance of not less than 100 metres from the face; d) Verify, before carrying out a blast, that an alarm with a range greater than 500 metres around the site where it is to be carried out has been activated, to warn of the danger any person who may be in that area; e) Check that the alarm sounds continuously for at least 10 minutes before the blast begins and 10 minutes after the last hole is fired; f) Check that all workers have been withdrawn from the place where the blast is to be carried out, and g) Carry out blasting operations with personnel authorised for this activity.

9.7 Transport of workers

9.7.1 In open-pit mines, a procedure shall be in place for transporting workers in accordance with the vehicle used for that purpose, which shall include at least the following: a) The safe way of using and operating the vehicle; b) The communication system to be used; c) The maximum permitted speed, including its signage; d) The vehicle's safety instructions, and e) Traffic instructions.

9.7.2 In open-pit mines, the operating manuals for the vehicles used to transport workers shall be available; these shall be in the Spanish language and based on the manufacturer's instructions.

9.7.3 The safety procedures for transporting workers in open-pit mines shall be communicated to workers by means of signs, notices and posters strategically placed in the areas designated for personnel.

9.7.4 To keep the vehicles used to transport workers in safe operating condition, a programme for their inspection and maintenance shall be in place and monitored; it shall contain at least the activity to be carried out, its frequency, the dates on which it is carried out and the person responsible for its execution.

9.7.5 Open-pit mines shall keep a record of the results of the inspections and maintenance of the vehicles or equipment used.

9.7.6 Vehicles used for the regular transport of workers in open-pit mines shall have functional seats.

9.7.7 Workers shall only be transported in vehicles designed for this purpose or in cargo vehicles without materials, in accordance with the provisions of paragraph 9.7.11 of this Standard.

9.7.8 Operators of vehicles used to transport workers in open-pit mines shall inspect the safety condition of the vehicles before use, to detect anomalies, and shall report any faults detected, as applicable.

9.7.9 When transporting workers in open-pit mines, at least the following safety measures shall be adopted: a) Do not exceed the maximum established occupant capacity of the vehicles used for personnel transport; b) Mark and, where applicable, light the workers' boarding and alighting stations; c) Have vehicles fitted with sturdy sheet-metal roofs, perimeter protection and bars or handrails to hold on to; d) Operate the vehicles with workers trained and authorised for that purpose, and e) Withdraw from service any vehicles that show faults, for inspection and, where applicable, maintenance.

9.7.10 The transport of personnel shall be prohibited in open-pit mines under the following conditions: a) Outside cabins and on platforms without lateral protection; b) In tipping beds, and c) In the beds or platforms of vehicles loaded with any type of material.

9.7.11 The transport of personnel in cargo vehicles shall only be permitted in the event of an accident or imminent risk, or for justified extraordinary circumstances, when such vehicles have: a) Perimeter protection on the platform preventing the accidental fall of any worker; b) Devices allowing workers to hold on properly, and c) A platform or bed without a tipping mechanism.

9.8 Transport of materials

9.8.1 In open-pit mines, a safety procedure for the transport of materials shall be in place, taking into account at least the following: a) The equipment to be used for the transport of materials; b) The safe way of loading and unloading materials; c) The communication systems to be used; d) The maximum permitted speed, including its signage; e) Traffic instructions setting out the traffic priority of vehicles for: 1) The transport of personnel, and 2) The transport of materials, and f) Traffic instructions for: 1) Vehicles and/or equipment travelling on steep gradients, and 2) Major mobile equipment and emergency or rescue vehicles.

9.8.2 Operating manuals for the equipment used for the transport of materials shall be available to the operators of such equipment, including the corresponding safety procedures.

9.8.3 The safety instructions for the equipment used shall be communicated for compliance purposes, by means of signs, notices and posters strategically placed in the areas occupied by personnel.

9.8.4 In open-pit mines, a programme for the inspection and maintenance of self-propelled vehicles, machinery or equipment used for the transport of materials shall be in place, which shall: a) Be carried out at least once a year; b) Contain at least the activity to be carried out, its frequency, the dates on which it is carried out and the person responsible for its execution, and c) Have its results recorded.

9.8.5 Operators of self-propelled vehicles, machinery and equipment used for the transport of materials shall comply with the following: a) Have the corresponding work permit; b) Carry out a visual inspection of road conditions on winding and unstable terrain; c) Apply the procedure established for that purpose for loading, unloading and manoeuvring, so as not to exceed the load capacity of the unit; d) Periodically check and record the following general mechanical conditions: 1) Bodywork; 2) Brakes; 3) Lights; 4) Tyres, and 5) Integrity and operation of the switches, guards, protective devices and safety devices, and e) Report to the supervisor or the person in charge of the mine, for repair, any faults detected during the periodic inspection that compromise the safety of workers and facilities.

9.8.6 All material transport vehicles, whether wheeled or tracked, shall comply with the following: a) Have a braking system that ensures the vehicle stops and remains stationary with the maximum load and under any other operating condition; b) Have clearly visible front, rear and warning lights; c) Have an audible warning signal that activates automatically when the vehicle moves in reverse; d) Have the bed for transporting materials reinforced in such a way that it withstands the load and the impact of rocks or materials; e) Provide good visibility for the driver, even when the cabin is modified or fitted out; f) Have a comfortable seat that reduces equipment vibration for the driver, control devices with suitable fittings and access points; g) Have the engine exhaust outlet located away from the operator and, where applicable, from the air-conditioning intake, when diesel-engine equipment is used, and h) Have at least one 4.5 kg type ABC fire extinguisher.

9.8.7 For material transport activities in open-pit mines, at least the following safety measures shall be adopted: a) Leave the vehicle only when: 1) The engine is switched off, with the main switch in the “off” position; 2) The handbrake or its equivalent is applied; 3) Moving parts, such as buckets, blades, among others, are secured or lowered to ground level; 4) Its tyres are chocked with wedges, if it is parked on a slope, and 5) It is naturally held by a ridge in the terrain, in the case of a tracked vehicle; b) Verify that the roads in open-pit mines comply with the following: 1) They have a width suitable for the vehicles that will travel on them and a barrier or berm at the edge; 2) They have suitable widened sections for crossing and for overtaking at a distance, in the case of single-lane roads, such that they are always visible from both directions; 3) They have a gradient and radius, at any point on the road, such that vehicles can travel under safe conditions; 4) They are provided, at low points -of the mine roads- with the drainage necessary to prevent water from pooling; 5) They are systematically cleared of snow and ice, by spreading sand, gravel, slag or any other suitable material, when road conditions are such that the surface could freeze, and 6) They have emergency escape routes, when used to transport loads on gradients of more than 5%, which: i. Are spaced along the entire length of the haul road, and ii. Allow the vehicle taking the emergency escape route to stop; c) Have safety signs indicating the maximum speed at which vehicles may travel, taking into account road conditions, gradients, space, visibility, traffic and the type of material being transported; d) When transporting loads that project beyond the sides or the rear of the vehicle, fit the following at the projecting end of the load: 1) A warning light during night shifts or when visibility is limited, and 2) A visible warning flag of appropriate size, during the day, and e) Install signage in places where there is a height restriction above ground level.

9.8.8 Vehicles with diesel combustion engines shall only be refuelled at supply stations or by service vehicles fitted out for that purpose.

9.8.9 Vehicles powered by diesel combustion engines that show anomalies while running, additional engine noise, or especially when they emit noticeable smoke, throw off sparks, or show a water or fuel leak, shall be stopped immediately and withdrawn from service for repair.

9.8.10 The roads and routes travelled by vehicles in open-pit mines shall be signposted in accordance with NOM-026-STPS-2008, or any standard superseding it, indicating at least intersections, changes of direction and steep gradients.

9.8.11 In open-pit mines, when mobile cranes and overhead cranes are used, at least the following shall be complied with: a) Have safety procedures in place for operators on the operation of mobile cranes and overhead cranes, in accordance with the manufacturer's instructions; b) Verify that every crane, boom truck and similar material-handling equipment used in open-pit mines is installed, operated and maintained based on the manufacturer's instructions; c) Have a light-only alarm on mobile cranes, and a light and audible alarm on overhead cranes; d) In the use of cranes and other lifting devices, adopt at least the following safety measures: 1) That they are operated only by workers authorised and trained for this purpose; 2) That lifting devices and slings of characteristics suitable for hoisting the materials being transported are used; 3) That the lifting devices, slings, cables, ropes and other crane elements are verified to be in good condition; 4) That, where required, tag lines tied or attached to loads are fitted, so that, while the load remains suspended, it can be stabilised or guided; 5) That the area where a suspended load is located is delimited and signposted, to prevent workers and vehicles from passing beneath it, and 6) That no material is dropped from an elevated point unless the area onto which such material will fall has been cleared of workers and vehicles, and protective barriers and warning signs have been put in place, and e) Prohibit any modifications to the crane being made without the employer's authorisation and in accordance with the manufacturer's instructions.

9.9 Electrical installations

9.9.1 In open-pit mines, drawings of the mining operations shall be available, indicating the identification and location of transformers, main switches, electrical controls, distribution boards, pumps, as well as telephone and communications electrical circuits.

9.9.2 Electrical installation drawings shall comply with the following conditions: a) Be in the Spanish language; b) Specify the capacity of at least the transformers, battery chargers and circuit protections; c) Be available at the main substations and control rooms for workers to consult; d) Be updated monthly and whenever there are changes or new installations in the electrical power distribution; e) Bear the name and signature of the persons in charge of the maintenance, safety and operation area, and f) Be kept for a period of at least twelve months.

9.9.3 Electrical installation drawings shall include: a) An updated single-line diagram that includes, at least: 1) The voltages of the primary and secondary windings of the transformers; 2) The type of connections in the primary and secondary windings of each transformer; 3) The impedances and rated characteristics, in kV or MVA, of the transformers; 4) The number of phases; 5) The cable lengths between circuit elements; 6) The conductor sizes, including earthing conductors, in mm 2 or mcm (circular mil x10-3); 7) The capacity of the circuit breakers and the capacity of the branch-circuit protection, and 8) The calculation record supporting the size of the conductors to be used; the capacity of the overload and short-circuit protections; the phase balancing; the capacity of the circuits, and the characteristics of the electrical equipment to be used in the mine's electrical installations; b) The general load schedule; c) The emergency generators; d) The metering centres; e) The load centres or panels; f) The transfer switches, and g) Earth-fault detection devices or systems.

9.9.4 For the maintenance of electrical installations in open-pit mines, safety procedures shall be in place for: a) The placement of safety tags and padlocks; b) The installation of conductors and electrical equipment; c) The splicing or connection of cables; d) The discharge of residual voltages from installed equipment; e) Its inspection, including verification of the good condition of the branch-circuit protections; f) Verification of electrical continuity and measurement of the resistance of the earthing system, and g) Measurement of the insulation resistance of cables.

9.9.5 The safety procedures for the maintenance of electrical installations shall include at least the following: a) Instructions for applying safety measures; b) The sequence of actions that personnel shall carry out for the activity; c) The type of tools, instruments or measuring equipment to be used; d) The personal protective equipment that the worker shall wear and use, where applicable, and e) Instructions for acting in the event of an emergency.

9.9.6 In open-pit mines, an annual programme for the inspection and maintenance of electrical installations shall be in place, the activities of which shall be carried out in accordance with NOM-029-STPS-2011 or any standard superseding it, and shall include the following: a) The activity to be carried out as a result of the inspection of the electrical installations; b) The equipment subject to inspection or maintenance; c) The code or identification number of the equipment subject to inspection or maintenance, where applicable; d) The procedure for the placement of safety tags and padlocks; e) The safety measures to be adopted; f) The frequency of the activity; g) The start and completion dates, and h) The person responsible for the activity.

9.9.7 The record of the results of the electrical installation inspection and maintenance programmes shall contain at least the following information: a) The equipment, device or connection subject to maintenance; b) The date on which the activity is scheduled; c) The date on which the activity is carried out; d) The type of activity carried out; e) The results of the activity carried out; f) The code or identification number of the activity carried out, where applicable, and g) The name of the person responsible for the activity.

9.9.8 The electrical installations of open-pit mines shall be approved by an electrical or electromechanical engineer.

9.9.9 The electrical installations of open-pit mines shall comply with at least the following: a) Install the cables of the signal and telephone systems independently and separately from the cables of the power and lighting systems; b) Protect the cables of the signal and telephone systems against any contact with any conduit or apparatus and against any induction effect; c) Have an earthing system to discharge: 1) Currents generated by insulation faults or by other types of electrical faults, and 2) Static electricity generated by the processes, to prevent electrical hazards to workers and equipment, as well as the risk of fire or explosion; d) Evaluate the operation of the earthing system at least once a year, in accordance with NOM-022-STPS-2008, or any standard superseding it; e) Have protections on the installed electrical equipment against overload, short circuit, earth fault and phase loss; f) Have identification on the switches and electrical equipment, painted or by means of self-adhesive labels, indicating at least the operating voltage, as well as the circuit or equipment they supply; g) Have physical protections that prevent workers from coming into contact with the surface and connection terminals of the equipment, and h) Have devices that cut off power to the entire electrical installation and/or devices that cut off power by branch circuit.

9.9.10 The control devices of the electrical installations shall comply with at least the following: a) Be fitted with switches that facilitate control of the power and, when necessary, isolation; b) Have signage indicating the units they control, in the case of the main switching devices and terminals; c) Allow that, when a motor operating under remote control is stopped from any location, it can only be restarted from the same location where it was stopped, and d) Have, in the case of mobile equipment driven by electric motors that are remotely controlled, the following: 1) Safety switches, signposted and located within reach of the workers who work alongside such equipment. These switches shall prevent the motor from starting until the switch has been manually closed, and 2) Emergency stop devices with mechanical interlocking, located next to the equipment itself and within reach of workers.

9.9.11 The distribution boxes of the electrical installations of open-pit mines shall be: a) Fitted with switches for each branch circuit, which shall be equipped or designed in such a way that it can be visually determined whether the device is open and the circuit disconnected, and b) Labelled in such a way that it can be seen which circuit each device controls.

9.9.12 Electrical transformer substations installed in open-pit mines shall comply with the following: a) Be located at distances greater than 50 metres from any quantity of explosives for immediate use; b) Have at least one 9 kg type ABC fire extinguisher or its equivalent; c) Have overcurrent or other fault protection devices on each low-voltage branch circuit; d) Have a connection to an effective earthing system; e) Have protective railings to prevent and control the passage of personnel, equipment or materials, and f) Be signposted, based on NOM-026-STPS-2008, or any standard superseding it.

9.9.13 The supply cables of mobile or portable electrically-powered machinery shall comply with the following: a) Be of the flexible type; b) Be heavy-duty; c) Be firmly secured to the machinery to prevent their terminals from being damaged or accidentally disconnected; d) Be positioned in such a way that they are not mechanically strained, and e) Be kept on supports designed for that purpose in the case of additional extensions.

9.9.14 The cables used in open-pit mines shall comply with the following: a) Be heavy-duty; b) Satisfy the electrical characteristics shown on the drawings and in the calculation record attached to the single-line diagrams; c) Be of the flexible type and of the size required to prevent overheating from electrical load, in the case of the electrical cables used to connect portable electrical equipment; d) Be protected from moisture and kept away from contact with water pipework; e) Be installed in such a way that they do not suffer mechanical damage, and f) The use of bare cables to supply electrical equipment is prohibited.

9.9.15 The areas where transformers or substations are located in open-pit mines shall have safety signs, in accordance with NOM-026-STPS-2008 or any standard superseding it, indicating at least the following: a) That they are in operation and/or energised; b) The mandatory use of personal protective equipment for personnel entering, where applicable, and c) The prohibition of access to the area by unauthorised persons.

9.9.16 Only personnel trained and authorised by the employer shall carry out work on the electrical installations.

9.9.17 Maintenance work on the electrical installations of open-pit mines shall be carried out in accordance with NOM-029-STPS-2011, or any standard superseding it.

9.10 Machinery and equipment

9.10.1 In open-pit mines, an up-to-date list shall be kept of the machinery and equipment used for exploration, mining, extraction and transport activities of workers and materials, indicating for each item at least the following: a) Its asset number or corresponding identification; b) A general description of its use, and c) The type of fuel or energy used.

9.10.2 The operation and maintenance of the machinery and equipment used in open-pit mines shall be carried out only by personnel authorised and trained by the employer for that purpose.

9.10.3 Machinery and equipment for open-pit mining shall be used in accordance with the manufacturer's instructions and only for the activities for which they were designed.

9.10.4 For the operation and maintenance of machinery and equipment, work procedures shall be in place containing the applicable safety measures and prohibitions, in accordance with the corresponding risk analysis.

9.10.5 In open-pit mines, a maintenance programme for machinery and equipment shall be in place, taking into account at least: a) The asset number or corresponding identification of the machinery or equipment; b) The scheduled dates for carrying out maintenance; c) The maintenance routines, including verification of the safety devices, and d) The signature of the person responsible for scheduling the activity.

9.10.6 The record of the results of the maintenance programmes for machinery and equipment shall contain at least the following information: a) The date on which the activity is carried out; b) The type of activity carried out; c) The results of the activity carried out, and d) The name of the worker who carried out the activity.

9.10.7 The safety procedures for carrying out maintenance activities on machinery and equipment used in open-pit mines shall take into account at least the following: a) The safety measures to be adopted in the area where maintenance is carried out, such as cordoning off and signposting the area, among others; b) The safety measures to be applied to the machinery or equipment during maintenance, such as cutting off power, placing safety padlocks and tags, among others; c) The equipment, tools and substances to be used; d) The personal protective equipment that the worker carrying out the maintenance shall wear, and e) The authorisations that the worker shall obtain prior to carrying out the work, where applicable.

9.10.8 On the moving parts of machinery and equipment with a risk of entanglement or mechanical pinching, fixed guards or protective covers shall be in place to prevent injury to personnel.

9.10.9 The guards and protective devices of the machinery and equipment, including emergency stop devices, shall be kept in operating condition at all times.

9.10.10 When workers have to access certain areas or confined spaces within a machine or equipment with moving parts, to carry out activities related to its operation or maintenance, an energy isolation (lockout) or de-energisation and signage procedure developed for that purpose shall be applied, ensuring that the machine or equipment cannot be inadvertently started up until the worker who isolated the machine or equipment removes the protection.

9.10.11 When workers may be at risk from moving around or carrying out activities near machines, the work area shall be signposted and delimited.

9.11 Flooding

9.11.1 The hydrological study referred to in paragraph 9.1.1, item c), of this Standard, shall contain at least the following: a) Drawings of the extraction operations, with the location of the aquifers close to the mining operation site and surface water bodies (rivers, lakes, among others), and b) The determination of the minimum permitted proximity limits to aquifers for mining, based on the geotechnical study, and the topography and geology of the site.

9.11.2 The hydrological study of open-pit mines shall be updated when: a) The extraction processes are modified; b) New areas to be mined are evaluated towards areas not considered in the study, and c) The results of the inspections indicate unusually high frequencies and quantities of water seepage into the mine.

9.11.3 Places at risk of flooding shall be marked on the location drawings of the water accumulation zones near the mining areas and made known to workers.

9.11.4 Prevention and control measures against flooding shall be determined, where applicable, taking as a reference the results of the hydrological study, which shall contain at least the following: a) The characteristics of the protective barriers or pillars between the mining operation and the body of water or, where applicable, an old mine working; b) The operating procedures for the advance of extraction and the preservation of the protective barrier or pillar; c) The characteristics of the pumping system, and d) The emergency response plan, based on what is determined in Chapter 13 of this Standard.

9.11.5 Before starting an excavation, and in accordance with the results of the hydrological study, preventive measures shall be determined, which shall contain at least the following: a) Leave protective barriers or pillars between the mining operation and the body of water, when mining operations take place in the vicinity of rivers, lakes and seas or of flooded underground mines; b) Ensure that no mining operation is carried out within the limits of the protective pillars, and c) Apply the specific procedure, developed for that purpose, for carrying out activities in the vicinity of the limits of the protective pillars.

10.1 Every person entering the exploration and mining areas of underground or open-pit mines shall wear the following personal protective equipment: a) Safety helmet; b) Protective footwear with toe caps or, where applicable, rubber boots with toe caps; c) Ear plugs or ear muffs; d) Gloves; e) Safety glasses; f) Particulate respirator; g) Work clothing made of cotton or of materials that do not generate static electricity, and h) Metal identification tag.

10.2 Persons entering underground mines shall, in addition to what is indicated in the previous paragraph, wear the following: a) A miner's lamp with a rechargeable battery lasting at least 1.25 times the worker's shift; b) A lamp belt, and c) A self-rescuer.

10.3 The specific personal protective equipment worn by workers in underground or open-pit mines shall be selected in accordance with the risk analysis for the identification of hazards and control of risks, and in accordance with NOM-017-STPS-2008, or any standard superseding it.

10.4 In underground and open-pit mines, procedures shall be in place for the use, inspection, replacement, cleaning, limitations, maintenance, storage and final disposal of personal protective equipment, based on the manufacturer's information, and based on the provisions of NOM-017-STPS-2008, or any standard superseding it.

10.5 In underground and open-pit mines, it shall be verified that workers maintain, store, clean and, where applicable, replace personal protective equipment, in accordance with the corresponding specific instructions.

11.1 In underground and open-pit mines, written authorisation (permit to work) shall be given only to trained workers - in accordance with the corresponding safety procedures - to carry out the following activities: a) Operation and maintenance of: 1) Locomotives; 2) Major machinery; 3) Major mobile equipment; 4) Vehicles of any type travelling inside the underground mine and in the stopes; 5) Electrical installations, and 6) Motorised winches, and b) Receipt, storage, transport, handling or use of explosives.

11.2 The authorisations shall contain at least the following: a) The name of the authorised worker; b) The type of work to be carried out; c) The area or place where the work will be carried out; d) The risk factors identified in the analysis of the prevailing conditions in the area where the work will be carried out; e) The safety measures to be applied in accordance with the work to be performed; f) The date and time work is to begin; g) The estimated duration of the work, and h) The name and signature of the employer or of the person designated by the employer to grant the authorisation.

11.3 Underground and open-pit mines shall keep a record of the authorisations granted to workers.

12.1 The programme for health surveillance of occupationally exposed personnel shall consider at least the following: a) The application of pre-employment medical examinations; b) The performance of annual periodic medical examinations including at least: complete blood count, postero-anterior chest X-ray, spirometry and pure-tone audiometry; c) The performance of medical examinations, based on the specific activity of the occupationally exposed personnel or, where applicable, on what is established by the official Mexican standards issued in this regard by the Ministry of Health; d) The health assessment of workers who carry out activities inside underground mines and in open-pit mines, which shall consider at least the worker's clinical history and physical examination, as well as the medical examinations performed; e) The performance of health check-ups on workers, in cases where the worker's clinical presentation warrants it and the company physician so determines; f) The application of preventive and corrective actions for health surveillance of occupationally exposed personnel, in accordance with the risk factors detected and the results of the medical examinations performed; g) The safekeeping of the medical examinations performed and their records, as well as of the preventive and corrective actions for health surveillance of workers, and h) The retention of clinical records for a minimum period of five years, counted from the date of the last medical act.

12.2 The programme for health surveillance of occupationally exposed personnel shall be signed by the employer and endorsed by the occupational safety and health prevention services.

12.3 Health surveillance of occupationally exposed personnel shall be carried out by a physician.

13.1 Each mining unit shall have a written emergency response plan that complies with the following: a) Be available at the mine office for workers to consult, and b) Be approved and signed by the employer, as well as by the person in charge of the occupational safety and health prevention services.

13.2 The emergency response plan shall contain at least the following: a) The organisation of one or more emergency response teams or crews to deal with fire, flood or collapse emergencies, as well as rescue and recovery, evacuation and first aid; b) The person responsible for implementing or coordinating the emergency response plan and/or the activities of the emergency response teams; c) The alert, alarm and emergency response procedures, indicating: 1) The means that persons will use to raise the alert; 2) The immediate actions for responding to the emergency; 3) Firefighting; 4) Evacuation of the mine; 5) First aid; 6) Rescue and recovery; 7) Coordination of the mine's emergency response teams with external ones; 8) Control of access to the mine, and 9) Re-entry into the mine; d) Procedures indicating: 1) To whom or where personnel shall report after raising the alarm; 2) The functions, responsibilities and actions to be carried out during and after the emergency by each member of the emergency response teams, and 3) The maximum length of time personnel may remain in the mine; e) The personal protective equipment for each of the emergency response teams, according to the emergency that may occur and in accordance with NOM-017-STPS-2008, or any standard superseding it; f) A programme for inspecting the equipment and systems required for each of the emergency response teams or crews, so that they are at all times fit for use and in good operating condition; g) A first aid kit containing the materials required to provide care to injured persons according to the type of risk that may occur; h) The inventory, location and copy of the latest inspection of the emergency equipment, as well as of the rescue systems and equipment; i) The location of the operations and aid centres in the event of an emergency; j) The annual medical examinations that members of the emergency response teams or crews shall undergo; k) The training that members of the emergency response teams shall receive in relation to the emergency response plan and to each of the emergencies that may occur; l) The emergency response drills carried out by the emergency response teams and the recording of their results, at least every three months, covering fires, floods or collapses; m) The evacuation drills, which shall be carried out at least once a year, based on the procedures referred to in item c) of this paragraph, in which all workers shall take part, and n) The evaluation and feedback of the emergency response plan, including the results of the drills carried out, the exercises carried out by the emergency response teams and, where applicable, the measures necessary to improve the emergency response plan.

13.3 The document relating to the organisation of the emergency response teams under the emergency response plan shall include the name, position, shift, functions and responsibilities of their members.

13.4 The procedures of the emergency response plan shall contain: a) The functions to be carried out; b) The responsibilities and actions during and after the emergency, and c) The length of time personnel may remain, and the declaration of the emergency status.

13.5 The emergency alert and alarm procedures shall consider at least the following conditions: a) That there are two fully independent alarm systems, which are redundant; b) That the emergency alarm system contains a specific code known to all workers, for the purpose of signalling evacuation in the event of an emergency, and c) That the emergency alarm system has a range that ensures all workers in the mine are alerted.

13.6 The alert and alarm procedures shall contain, for each type of emergency, at least the following criteria: a) That the nearest supervisor is immediately notified of the condition detected; b) That the person in charge of activating the alarm is notified immediately, in accordance with the established instructions; c) That the person who notices the emergency at its onset attempts to contain it, if possible and if trained to deal with it; d) That the instructions for activating the alarm and responding to the emergency are followed; e) That the personnel monitoring from the surface and any persons who may be affected inside the mine are informed, and f) That personnel, on receiving the alarm, evacuate the mine immediately and, if this is not possible, go to the nearest refuge.

13.7 The emergency response procedures shall consider at least the following criteria: a) That when the emergency alarm is raised, the persons authorised to enter the mine to respond to the emergency coordinate their activities; b) That the application of the emergency response procedures is supervised; c) That when workers are ordered to be evacuated immediately from the areas threatened by the emergency, only those necessary to control or combat it, where applicable, are allowed to remain; d) That first aid is given to the injured worker until they receive the required medical attention, and that medication is administered only under medical prescription and supervision; e) That, for rescue and recovery, the affected areas are assessed before acting; f) That the names of all workers inside the mine can be known at all times; g) That access to the mines is for authorised workers, and that visitors are only allowed access to the interior of the mine when accompanied by authorised workers; h) That in cases of serious and imminent risk, activities are suspended, partially or totally, until the situation has been brought under control, and i) That, for re-entry into the mine, it is provided that workers shall only be allowed to return to work once the emergency has been brought under control and the emergency response team members and the personnel of the occupational safety and health prevention services have assessed that the mine has safe and healthy conditions.

13.8 The rescue equipment and the personal protective equipment of the emergency response team members shall be located in accordance with the results of the risk analysis, and shall be signposted in accordance with NOM-026-STPS-2008, or any standard superseding it. The location of the equipment shall be checked by the emergency response teams at least once a month.

13.9 Emergency response team members shall be provided with information on the inventory and location of the equipment available for responding to emergencies, and the location of the operations and aid centres for emergency situations.

13.10 The record of the results of the emergency response drills and exercises shall contain at least the following: a) The problems detected; b) The proposals for improvement, and c) The name and signature of the person designated by the employer to keep the record.

14.1 New workers shall be given induction training on the general occupational safety and health conditions to be complied with in the different areas of the mining units.

14.2 All workers shall be provided with training, instruction and information based on their assigned tasks and the emergency response plan.

14.3 The training and instruction provided to workers shall cover at least the following: a) The official Mexican standards on occupational safety and health applicable to the mining unit; b) Information on the occupational hazards related to the activity they perform; c) The safety procedures and work instructions for carrying out their activities; d) The safety measures established in this Standard, applicable to the activities to be carried out, and which shall be adopted when carrying out the activities; e) The use, maintenance, upkeep, storage and replacement of personal protective equipment, in accordance with NOM-017-STPS-2008, or any standard superseding it; f) The theoretical and practical topics on the safe way to handle, inspect, maintain and store machinery, equipment, tools, materials and work implements; g) The criteria applicable to machinery, equipment, tools, materials and work implements, for determining that they are taken out of service for repair or replacement; h) The adverse conditions that could arise in the work areas, in the machinery and equipment, in the personal protective equipment and, where applicable, weather conditions or other unfavourable factors that would require work to be interrupted; i) The content of the emergency response plan and other actions arising from emergency situations, and j) The use and, where applicable, replacement of self-rescuers in emergency situations, at least every six months.

14.4 Training and instruction for workers shall be provided whenever the work processes, the equipment they use or their regular activity changes.

14.5 Specific training shall be provided to members of the emergency response teams or crews for dealing with fire, flood or collapse emergencies.

15.1 In underground and open-pit mines, a record of occupational accidents shall be kept, containing at least the following: a) The general details of the injured person; b) The type of accident or incident that occurred; c) The frequency and severity indicators; d) The statistics of occupational accidents, according to the activities involved, and e) Follow-up on the safety measures adopted after an accident, in accordance with the results of the investigation.

15.2 When an accident or incident occurs, an investigation shall be carried out, covering at least the following: a) The identification of the injured person; b) The causes of the accident, including, among others, the hazardous or unsafe conditions and/or unsafe acts that caused it; c) The consequences of the accident, specifying the part of the body injured, and the type of injury and/or material damage caused; d) The evaluation of the accident; e) The result of the investigation; f) The proposed safety measures to be adopted, in the short or long term, based on the results of the investigation, to prevent the accident from recurring, and g) Follow-up on the accident and the safety measures implemented.

15.3 In underground and open-pit mines, a record shall be kept of the investigations of accidents and incidents that have occurred and of the evaluation of their conditions.

16.1 The employer may engage an accredited and approved verification unit, under the terms of the Federal Law on Metrology and Standardisation and its Regulations, to verify the degree of compliance with this Standard.

16.2 Verification units assessing conformity with this Standard shall apply the compliance criteria established in the conformity assessment procedure in Chapter 17 of this Standard.

16.3 Accredited and approved verification units assessing compliance with this Standard shall issue a verification report, which shall contain: a) Employer details: 1) The name, denomination or corporate name; 2) The full address, and 3) The name and signature of the employer and, where applicable, of the legal representative, and b) Verification unit details: 1) The name, denomination or corporate name; 2) The registration number granted by the accreditation body; 3) The approval number granted by the Ministry of Labour and Social Welfare; 4) The dates on which accreditation and approval were granted; 5) The result of the verification; 6) The name and signature of the person responsible for issuing the verification report; 7) The place and date of signature of the verification report; 8) The validity period of the verification report, and 9) The registration number of the verification report granted by the Ministry of Labour and Social Welfare, when the corresponding report is submitted.

16.4 The validity period of the verification reports issued by the verification units shall be one year, provided that the conditions on which their issuance was based are not modified.

17.1 This conformity assessment procedure applies both to inspection visits carried out by the labour authority and to verification visits carried out by the verification units.

17.2 The current verification report shall be available to the labour authority when requested.

17.3 The aspects to be verified during the conformity assessment of this Standard shall be carried out, as applicable, by means of physical verification, documentary review, records or interviews, in accordance with the following: Type of

5.1 and 7 Documentary The employer complies when it submits documentary evidence that:  Has the risk analysis for the Serious identification of hazards and control of risks;  The risk analysis for the identification of Serious hazards and control of risks includes the determination of the magnitude of the risk (MR) and the controls necessary for its prevention, protection and control;  The risk analysis for the identification of Serious hazards and control of risks is:  Up to date;  Available to workers, and  Approved and signed by the employer and the person in charge of the occupational safety and health prevention services;  The risk analysis for the identification of Serious hazards and control of risks is reviewed when:  The exploration, mining, ground support, ventilation system and electrical installation processes are modified, as applicable;  Any change is made that may alter the safety conditions and procedures, and  The risks to workers or to the workplace are modified;  The risk analysis for the identification of Serious hazards and control of risks takes into account, as applicable, the following:  The analysis of activities by process, area or job position, which includes at least: o Routine and non-routine activities, and o The activities of all persons who have access to the workplace, including contractors and visitors;  Installations that may generate hazards;  The infrastructure, equipment and materials at the workplace, in particular the safety and operating characteristics and conditions of the machinery, equipment and tools to be used;  Hazardous chemical substances that are

5.2 Documentary The employer complies when it submits documentary evidence that:  Has, where applicable, a study that guarantees Serious that the self-rescuers allow workers to reach the surface from the most remote point of the underground mine, or to take refuge in a safe shelter, and, where applicable, has reserve or additional self-rescuers, in accordance with the following:  Provides one self-rescuer for each of the workers who are inside the mine;  Distributes the reserve or additional self-rescuers in strategic locations; Type of

5.3 Documentary The employer complies when it submits documentary evidence that it draws up and monitors a programme for the review and maintenance of the equipment, machinery and/or vehicles used, which contains at least the scheduled date, the activity to be carried out, the date on which it is carried out and the person responsible for its execution.

5.4 Documentary The employer complies when it submits documentary evidence that it has safety procedures for performing exploration and exploitation activities, drafted in the Spanish language.

5.5 and 8 Documentary The employer complies when it submits documentary evidence that:  Before work in mines Serious underground is carried out, it has, at least, the following studies:  Geotechnical: rock mechanics or soil mechanics;  Geological, to locate faults and rock types, and  Hydrological, to assess flooding risks, together with the control procedures;  The geotechnical, geological and Serious hydrological studies are updated when the original conditions that were taken into account for their preparation are modified or altered;  The geotechnical, geological and Serious hydrological studies are kept for the operating life of the mine;  It has plans of the mining operations, Serious that meet the following conditions:  They are updated based on the progress of the works;  They are approved and signed by the employer, as well as by the person in charge of the occupational health and safety preventive services, and  They are available at the mine office for consultation by personnel;  The plans of the mining operations contain Serious as a minimum the following information:  The longitudinal sections showing the shafts, crosscuts, galleries, exploration and extraction faces, stopes, backfills and other underground mine workings;  The surface profile of the mine, with the location of subsidence areas and any known aquifer;  The location of pumping stations and hoists;  The mine ventilation, showing: o Air velocity and direction; o The location of the ventilation equipment; o The doors and elements required to control it, and o The interconnection points with other mines; Type of

4.5 kg, and  a miner's lamp; Type of

                                        materials         incombustible,         with
                                        coatings      incombustible    or     of

5.5 and 9 Documentary The employer complies when it presents documentary evidence that:  Before work is carried out in Serious open-pit mines, it has, at least, the following studies:  Geotechnical: rock mechanics or soil mechanics;  Geological, to locate faults and rock types, and  Hydrological, to assess flood risks, together with the procedures for their control;  The geotechnical, geological and Serious hydrological studies are updated when the original conditions taken into account for their preparation are modified or altered;  The geotechnical, geological and Serious hydrological studies are kept for the operational life of the mine;  It has plans of the Serious mining operations that meet the following characteristics:  They are updated in accordance with the progress of the works;  They are approved and signed by the employer, as well as by the person in charge of the occupational health and safety preventive services, and  They are available at the mine office for consultation by personnel;  The mining operations plans contain, Serious, at least the following:  Topographic information indicating the roads, ore-dumping and overburden-dumping areas, as well as the disposal areas;  The surface profile, including subsidence;

                                           establish      the     conditions    and
                                           procedures         of      safety

5.6 Documentary The employer complies when it submits evidence Serious documentary that it designates an engineer legally authorised to practise, as provided in article 34 of the Ley Minera, as responsible for compliance with this Standard. Type of

5.7 --------------- The employer complies when it submits evidence that This provision

5.8 Documentary The employer complies when it submits documentary evidence that:  It carries out an inspection of the conditions of Serious safety of the working faces in underground mines and of the pits in open-pit mines, in each work shift, and  The inspection to ensure the safety of Serious the workers takes into account, at least, the following:  In underground mines, the safety conditions relating to ground support, ventilation and the equipment used for breaking the material, and  In open-pit mines, the safety conditions relating to slope stability and major machinery.

5.8 Record The employer complies when it has a record of the Serious results of the inspections, and these record the signature of the supervisors of the outgoing and incoming shifts.

5.9 Record The employer complies when it has a Serious system for recording, for each work shift, the entry and exit of workers from the underground mine, and identifies their location by areas or zones on a plan at all times, preferably in real time.

5.10 and 8.14 Physical The employer complies when, during a walk-through inspection of the Serious workplace, it is verified that fixed or mobile refuge chambers are installed and available for use inside underground mines. Documentary The employer complies when it submits documentary evidence that  The size, number and Serious location of the refuge chambers inside underground mines is determined on the basis of:  The analysis carried out annually to identify hazards and control risks;  The probability of fires or collapses occurring, and  The advance of the working faces;  For the installation of the refuge chambers, at Serious least, the following is taken into account:  That the minimum and maximum distance from the refuge chambers to the workplaces is a function of the risk analysis for hazard identification and risk control, and  That they are located more than 60 metres from the powder magazines, and Type of

5.11 Documentary The employer complies when it submits documentary evidence that it has safety data sheets (SDS) for all the hazardous chemical substances used, in accordance with the provisions of NOM-018-STPS-2000, or the standard that replaces it.

5.12 Documentary The employer complies when it submits evidence Serious documentary that it constitutes, integrates and organises the health and safety commission(s) and oversees their operation, in accordance with the provisions of NOM-019-STPS-2011, or the standard that replaces it.

5.13 Documentary The employer complies when it submits evidence Serious documentary that it observes the provisions of NOM-020-STPS-2011, or the standard that replaces it, in the case of pressure vessels, cryogenic vessels and steam generators or boilers.

5.14 Documentary The employer complies when it submits documentary evidence that it notifies the Ministry of Labour and Social Welfare of occupational accidents occurring in the workplace, on the basis of the provisions of NOM-021-STPS-1993, or the standard that replaces it.

5.15 Physical The employer complies when, during a walk-through inspection of the Serious workplace, it is verified that:  In the areas of the mining units it has prohibition, mandatory action, caution and information signage, as applicable, in accordance with the provisions of NOM-026-STPS-2008, or the standard that replaces it, and  The signage indicates:  The hazards for each area of the mining unit;  The use of personal protective equipment, and  The evacuation routes with elements indicating the direction of the exit, as well as safety signs or notices that have, where applicable, reflective or fluorescent materials.

5.16 Documentary The employer complies when it submits documentary evidence that it carries out welding and cutting activities, as established by NOM-027-STPS-2008, or the standard that replaces it.

5.17 Documentary The employer complies when it submits evidence Serious documentary that it has the occupational safety and health prevention services referred to in NOM-030-STPS-2009, or the standard that replaces it. Type of

5.18 Documentary The employer complies when it submits documentary evidence that it carries out the construction of buildings, facilities or premises of the mining unit, in accordance with the provisions of NOM-031-STPS-2011, or the standard that replaces it.

5.19 and 10 Documentary The employer complies when it submits evidence Serious documentary that it provides workers with basic personal protective equipment and, where applicable, the specific equipment that corresponds to them, on the basis of the activity they carry out and the risks to which they are exposed. Physical The employer complies when, during a walk-through inspection of the workplace, it is verified that:  Every person entering the Serious exploration and exploitation zones of open-pit mines wears the following personal protective equipment:  Protective helmet;  Protective footwear with toecap or, where applicable, rubber boots with toecap;  Ear plugs or ear muffs;  Gloves;  Safety glasses;  Particulate respirator;  Cotton work clothing or clothing made of materials that do not generate static electricity, and  Metal identification tag, and  Persons entering underground Serious mines wear the following:  Protective helmet;  Protective footwear with toecap or, where applicable, rubber boots with toecap;  Ear plugs or ear muffs;  Gloves;  Safety glasses;  Particulate respirator;  Cotton work clothing or clothing made of materials that do not generate static electricity;  Metal identification tag;  Mining lamp with rechargeable battery with a minimum duration of 1.25 times the worker's shift;  Lamp belt, and  Self-rescuer. Documentary The employer complies when it submits documentary evidence that:  The specific personal protective equipment Serious worn by workers in underground or open-pit mines is selected in accordance with the risk analysis for hazard identification and risk control, and in accordance with the provisions of NOM-017-STPS-2008, or the standard that replaces it;  In underground and open-pit mines, procedures are in place for the use, inspection, replacement, cleaning, limitations, maintenance, safekeeping and final disposal of personal protective equipment, based on the manufacturer's information, and on the basis of the provisions of NOM-017-STPS-2008, or the standard that replaces it, and  In underground and open-pit mines it is verified that workers maintain, keep safe, clean and, where applicable, replace personal protective equipment, in accordance with the corresponding specific instructions. Type of

5.20 Physical The employer complies when, during a walk-through inspection of the Serious workplace, it is verified that it checks that workers use personal protective equipment while performing their normal and emergency activities.

5.21 and 11 Documentary The employer complies when it submits documentary evidence that:  In underground and open-pit mines, only trained workers are authorised in writing -in accordance with the corresponding safety procedures-, to carry out the following activities:  Operation and maintenance of: o Locomotives; o Major machinery; o Major mobile equipment; o Vehicles of any type travelling inside the underground mine and in the pits; o Electrical installations, and o Motorised hoists, and  Receipt, storage, transport, handling or use of explosives, and  The authorisations (permits to work) contain, at least, the following:  The name of the authorised worker;  The type of work to be carried out;  The area or place where the work will be carried out;  The risk factors identified in the analysis of the prevailing conditions of the area where the work will be carried out;  The safety measures that shall be applied in accordance with the work to be performed;  The date and time of commencement of the activities;  The estimated duration of the work, and  The name and signature of the employer or of the person designated to grant the authorisation.

5.22 and 12 Documentary The employer complies when it submits documentary evidence that:  It has a programme for health surveillance of Serious workers;  The programme for health surveillance of Serious occupationally exposed personnel takes into account, at least, the following:  The administration of pre-employment medical examinations;  The performance of annual periodic medical examinations that, at least, include: complete blood count, postero-anterior chest X-ray, spirometry and pure-tone audiometry;  The performance of medical examinations, on the basis of the specific activity of the occupationally exposed personnel or, where applicable, on the basis of what is established by the official Mexican standards issued in that respect by the Ministry of Health; Type of

5.23 and 13 Documentary The employer complies when it submits documentary evidence that:  It has an emergency response plan; Serious  The emergency response plan is Serious available for consultation and use by workers and emergency response team members;  The emergency response plan complies with the Serious following:  It is available at the mine office for consultation by workers, and  It is approved and signed by the employer, as well as by the person in charge of the occupational safety and health prevention services;  The emergency response plan contains, at Serious least, the following:  The formation of one or more emergency response teams or crews to combat fire, flood or collapse emergencies, as well as for rescue and salvage, evacuation and first aid;  The person responsible for implementing or coordinating the emergency response plan and/or the activities of the emergency response teams;  The alert, alarm and emergency response procedures, which indicate: o The means the persons will use to raise the alarm; o The immediate actions for responding to the emergency; o Firefighting; o Evacuation of the mine; o First aid; Type of

                               The alert and alarm procedures for the                             Serious
                                emergency       take into account,    at    least,     the

5.24 Physical The employer complies when, during a walk-through inspection of the workplace, it is verified that it provides workers with hygienic spaces for eating food that comply with the provisions of the official Mexican standards issued in that respect by the Ministry of Health.

5.25 Physical The employer complies when, during a walk-through inspection of the workplace, it is verified that it provides workers with drinking water services and sanitary facilities -toilets, urinals, showers, among others-, in sufficient quantity, on the basis of what is determined by the official Mexican standards issued in that respect by the Ministry of Health, or by the local and environmental legislation on the matter.

5.26 and 14 Documentary The employer complies when it submits documentary evidence that:  It provides training on occupational safety and health Serious to all workers, in accordance with the safety procedures relating to the activities they carry out;  New workers are Serious given induction on the general occupational safety and health conditions that must be met in the different areas of the mining units;  All workers are provided with Serious training, instruction and information on the basis of the tasks assigned and the emergency response plan; Type of

5.27 Documentary The employer complies when it submits documentary evidence that it informs all workers of the mining units about the risks to which they are exposed in respect of the activities they carry out, at least once a year, and persons who are not employees of the workplace, prior to their entry into the mines for any reason.

5.28 Record The employer complies when it has a record of the Serious information provided to all workers, which at least contains: the date on which the information was provided; the name and position of the workers to whom it was provided, and the name of the instructor. Type of

5.29 Documentary The employer complies when it submits documentary evidence that it follows up on reports of incidents, accidents, unsafe conditions and acts and/or actual or potential emergency situations, detected during the performance of the activities.

5.30 and 15 Documentary The employer complies when it submits documentary evidence that it carries out the investigation into accidents and disasters that have occurred so as to adopt the preventive and corrective measures that prevent their recurrence.

5.31 Documentary The employer complies when it submits documentary evidence that:  It assesses the conditions of the underground mine or Serious of the open-pit mine after a disaster has occurred, and  It authorises, where applicable, the entry of the emergency response teams, and Serious the return to activities after a disaster has occurred only when the conditions that guarantee the safety of workers exist once again.

5.32 Physical The employer complies when, during a walk-through inspection of the Serious workplace, it is verified that no persons under 18 years of age and no pregnant or breastfeeding women work inside an underground mine or an open-pit mine.

17.4 For the selection of workers to be interviewed to confirm compliance with the provisions set out in this procedure for the evaluation of conformity, the sampling criterion contained in Table 5 below shall apply: Table 5 Sampling by random selection Number of workers to Total number of workers interview 1-15 1 16-50 2 51-105 3 1 for every 35 workers More than 105 up to a maximum of 15

17.5 The documentary evidence or records referred to in this Standard may be presented in printed form or by electronic means, and shall be retained for at least twelve months, except in those cases where the Standard specifies a different validity period.

Enforcement of compliance with this Official Mexican Standard is the responsibility of STPS.

19.1 Ley Minera. Last reform published in the Diario Oficial de la Federación on 26 June 2006.

19.2 Reglamento Federal de Seguridad, Higiene y Medio Ambiente de Trabajo, published in the Diario Oficial de la Federación on 21 January 1997.

19.3 Code of practice of the International Labour Organization. Safety and health in open-pit mines, 1991.

This Official Mexican Standard does not concord with any international standard, as no such reference existed at the time it was drafted.

FIRST. This Official Mexican Standard shall enter into force one year after its publication in the Official Gazette of the Federation. SECOND. During the period referred to in the preceding article, employers shall comply with Official Mexican Standard NOM-023-STPS-2003, Work in mines - Occupational safety and health conditions, or shall make the adaptations necessary to observe the provisions of Official Mexican Standard NOM-023-STPS-2012, Underground mines and open-pit mines - Occupational safety and health conditions. In the latter case, the labour authority shall provide, at the request of interested employers, advice and guidance to implement their compliance, without employers becoming liable to penalties for non-compliance with the Standard in force. THIRD. From the date on which this Standard enters into force, Official Mexican Standard NOM-023-STPS-2003, Work in mines - Occupational safety and health conditions, published in the Official Gazette of the Federation of 2 October 2003, shall cease to have effect. Given in Mexico City, Federal District, on the twenty-fourth day of the month of September, two thousand twelve.- The Secretary of Labour and Social Welfare, Rosalinda Vélez Juárez.- Signature.