Jul. 28, 2025
The following definitions apply to this part. In addition definitions contained in any subpart of part 57 apply in that subpart. If inconsistent with the general definitions in this section, the definition in the subpart will apply in that subpart:
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Abandoned areas means areas in which work has been completed, no further work is planned, and travel is not permitted.
Abandoned mine means all work has stopped on the mine premises and an office with a responsible person in charge is no longer maintained at the mine.
Abandoned workings means deserted mine areas in which further work is not intended.
Active workings means areas at, in, or around a mine or plant where men work or travel.
American Table of Distances means the current edition of “The American Table of Distances for Storage of Explosives” published by the Institute of Makers of Explosives.
Approved means tested and accepted for a specific purpose by a nationally recognized agency.
Attended means presence of an individual or continuous monitoring to prevent unauthorized entry or access. In addition, areas containing explosive material at underground areas of a mine can be considered attended when all access to the underground areas of the mine is secured from unauthorized entry. Vertical shafts shall be considered secure. Inclined shafts or adits shall be considered secure when locked at the surface.
Authorized person means a person approved or assigned by mine management to perform a specific type of duty or duties or to be at a specific location or locations in the mine.
Auxilary fan means a fan used to deliver air to a working place off the main airstream; generally used with ventilation tubing.
Barricaded means obstructed to prevent the passage of persons, vehicles, or flying materials.
Barrier means a material object, or objects that separates, keeps apart, or demarcates in a conspicuous manner such as cones, a warning sign, or tape.
Berm means a pile or mound of material along an elevated roadway capable of moderating or limiting the force of a vehicle in order to impede the vehicle's passage over the bank of the roadway.
Blast area means the area in which concussion (shock wave), flying material, or gases from an explosion may cause injury to persons. In determining the blast area, the following factors, shall be considered:
(1) Geology or material to be blasted.
(2) Blast pattern.
(3) Burden, depth, diameter, and angle of the holes.
(4) Blasting experience of the mine.
(5) Delay system, powder factor, and pounds per delay.
(6) Type and amount of explosive material.
(7) Type and amount of stemming.
Blast site means the area where explosive material is handled during loading, including the perimeter formed by the loaded blastholes and 50 feet (15.2 meters) in all directions from loaded holes. A minimum distance of 30 feet (9.1 meters) may replace the 50-foot (15.2-meter) requirement if the perimeter of loaded holes is demarcated with a barrier. The 50-foot (15.2-meter) and alternative 30-foot (9.1-meter) requirements also apply in all directions along the full depth of the hole. In underground mines, at least 15 feet (4.6 meters) of solid rib, pillar, or broken rock can be substituted for the 50-foot (15.2-meter) distance. In underground mines utilizing a block-caving system or similar system, at least 6 feet (1.8 meters) of solid rib or pillar, including concrete reinforcement of at least 10 inches (254 millimeters), with overall dimensions of not less than 6 feet (1.8 meters) may be substituted for the 50-foot (15.2-meter) distance requirement.
Blasting agent means any substance classified as a blasting agent by the Department of Transportation in 49 CFR 173.114(a) (44 FR , May 31, ) which is incorporated by reference. This document is available for inspection at each Metal and Nonmetal Mine Safety and Health District Office of the Mine Safety and Health Administration, and may be obtained from the U.S. Government Printing Office, Washington, DC .
Blasting area means the area near blasting operations in which concussion or flying material can reasonably be expected to cause injury.
Blasting cap means a detonator which is initiated by a safety fuse.
Blasting circuit means the electrical circuit used to fire one or more electric blasting caps.
Blasting switch means a switch used to connect a power source to a blasting circuit.
Blowout means a sudden, violent, release of gas or liquid due to the reservoir pressure in a petroleum mine.
Booster means any unit of explosive or blasting agent used for the purpose of perpetuating or intensifying an initial detonation.
Booster fan means a fan installed in the main airstream or a split of the main airstream to increase airflow through a section or sections of a mine.
Capped fuse means a length of safety fuse to which a blasting cap has been attached.
Capped primer means a package or cartridge of explosives which is specifically designed to transmit detonation to other explosives and which contains a detonator.
Circuit breaker means a device designed to open and close a circuit by nonautomatic means and to open the circuit automatically on a predetermined overcurrent setting without injury to itself when properly applied within its rating.
Combustible means capable of being ignited and consumed by fire.
Combustible material means a material that, in the form in which it is used and under the conditions anticipated, will ignite, burn, support combustion or release flammable vapors when subjected to fire or heat. Wood, paper, rubber, and plastics are examples of combustible materials.
Company official means a member of the company supervisory or technical staff.
Competent person means a person having abilities and experience that fully qualify him to perform the duty to which he is assigned.
Conductor means a material, usually in the form of a wire, cable, or bus bar, capable of carrying an electric current.
Delay connector means a nonelectric short interval delay device for use in delaying blasts which are initiated by detonating cord.
Detonating cord means a flexible cord containing a solid core of high explosives.
Detonator means any device containing a detonating charge that is used to initiate an explosive and includes but is not limited to blasting caps, electric blasting caps and non-electric instantaneous or delay blasting caps.
Distribution box means a portable apparatus with an enclosure through which an electric circuit is carried to one or more cables from a single incoming feed line; each cable circuit being connected through individual overcurrent protective devices.
Electric blasting cap means a detonator designed for and capable of being initiated by means of an electric current.
Electrical grounding means to connect with the ground to make the earth part of the circuit.
Employee means a person who works for wages or salary in the service of an employer.
Employer means a person or organization which hires one or more persons to work for wages or salary.
Emulsion means an explosive material containing substantial amounts of oxidizers dissolved in water droplets, surrounded by an immiscible fuel.
Escapeway means a passageway by which persons may leave a mine.
Explosive means any substance classified as an explosive by the Department of Transportation in 49 CFR 173.53, 173.88 and 173.100 which are incorporated by reference. Title 49 CFR is available for inspection at each Metal and Nonmetal Mine Safety and Health District Office of the Mine Safety and Health Administration, and may be obtained from the U.S. Government Printing Office, Washington, DC .
Face or bank means that part of any mine where excavating is progressing or was last done.
Fire resistance rating means the time, in minutes or hours, that an assembly of materials will retain its protective characteristics or structural integrity upon exposure to fire.
Flame spread rating means the numerical designation that indicates the extent flame will spread over the surface of a material during a specified period of time.
Flammable means capable of being easily ignited and of burning rapidly.
Flammable gas means a gas that will burn in the normal concentrations of oxygen in the air.
Flammable liquid a liquid that has a flash point below 100 °F (37.8 °C), a vapor pressure not exceeding 40 pounds per square inch (absolute) at 100 °F (37.8 °C), and is known as a Class I liquid.
Flash point means the minimum temperature at which sufficient vapor is released by a liquid or solid to form a flammable vapor-air mixture at atmospheric pressure.
Geological area means an area characterized by the presence of the same ore bodies, the same stratigraphic sequence of beds, or the same ore-bearing geological formation.
Highway means any public street, public alley or public road.
High potential means more than 650 volts.
Hoist means a power driven windlass or drum used for raising ore, rock, or other material from a mine, and for lowering or raising persons and material.
Igniter cord means a fuse, cordlike in appearance, which burns progressively along its length with an external flame at the zone of burning, and is used for lighting a series of safety fuses in the desired sequence.
Insulated means separated from other conducting surfaces by a dielectric substance permanently offering a high resistance to the passage of current and to disruptive discharge through the substance. When any substance is said to be insulated, it is understood to be insulated in a manner suitable for the conditions to which it is subjected. Otherwise, it is, within the purpose of this definition, uninsulated. Insulating covering is one means for making the conductor insulated.
Insulation means a dielectric substance offering a high resistance to the passage of current and to a disruptive discharge through the substance.
Laminated partition means a partition composed of the following material and minimum nominal dimensions: 1⁄2-inch-thick plywood, 1⁄2-inch-thick gypsum wallboard, 1⁄8-inch-thick low carbon steel, and 1⁄4-inch-thick plywood, bonded together in that order (IME-22 Box). A laminated partition also includes alternative construction materials described in the Institute of Makers of Explosives (IME) Safety Library Publication No. 22, “Recommendations for the Safe Transportation of Detonators in a Vehicle with Other Explosive Materials” (May ), and the “Generic Loading Guide for the IME-22 Container” (October ). The IME is located at 19th Street NW., Suite 310, Washington, DC -; 202-429-; https://www.ime.org. This incorporation by reference has been approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies are available at MSHA's Office of Standards, Regulations, and Variances, 201 12th Street South, Arlington, VA -; 202-693-; and at all Metal and Nonmetal Mine Safety and Health District Offices, or available for inspection at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.
Lay means the distance parallel to the axis of the rope in which a strand makes one complete turn about the axis of the rope.
Loading means placing explosive material either in a blasthole or against the material to be blasted.
Low potential means 650 volts or less.
Magazine means a facility for the storage of explosives, blasting agents, or detonators.
Main fan means a fan that controls the entire airflow of the mine, or the airflow of one of the major air circuits.
Major electrical installation means an assemblage of stationary electrical equipment for the generation, transmission, distribution, or conversion of electrical power.
Mantrip means a trip on which persons are transported to and from a work area.
Mill includes any ore mill, sampling works, concentrator, and any crushing, grinding, or screening plant used at, and in connection with, an excavation or mine.
Mine atmosphere means any point at least 12 inches away from the back, face, rib, and floor in any mine; and additionally, in a Category IV mine, at least 3 feet laterally away from the collar of a borehole which releases gas into a mine.
Mine opening means any opening or entrance from the surface into a mine.
Misfire means the complete or partial failure of a blasting charge to explode as planned.
Mobile equipment means wheeled, skid-mounted, track-mounted, or rail-mounted equipment capable of moving or being moved.
Multipurpose dry-chemical fire extinguisher means an extinguisher having a rating of at least 2-A:10-B:C and containing a nominal 4.5 pounds or more of dry-chemical agent.
Noncombustible material means a material that, in the form in which it is used and under the conditions anticipated, will not ignite, burn, support combustion, or release flammable vapors when subjected to fire or heat. Concrete, masonry block, brick, and steel are examples of noncombustible materials.
Non-electric delay blasting cap means a detonator with an integral delay element and capable of being initiated by miniaturized detonating cord.
Outburst means the sudden, violent release of solids and high-pressure occluded gases, including methane in a domal salt mine.
Overburden means material of any nature, consolidated or unconsolidated, that overlies a deposit of useful materials or ores that are to be mined.
Overload means that current which will cause an excessive or dangerous temperature in the conductor or conductor insulation.
Permissible means a machine, material, apparatus, or device which has been investigated, tested, and approved by the Bureau of Mines or the Mine Safety and Health Administration, and is maintained in permissible condition.
Potable water means water which shall meet the applicable minimum health requirements for drinking water established by the State or community in which the mine is located or by the Environmental Protection Agency in 40 CFR part 141, pages 169-182 revised as of July 1, . Where no such requirements are applicable, the drinking water provided shall conform with the Public Health Service Drinking Water Standards, 42 CFR part 72, subpart J, pages 527-533, revised as of October 1, . Publications to which references are made in this definition are hereby made a part hereof. These incorporated publications are available for inspection at each Metal and Nonmetal Mine Safety and Health District Office of the Mine Safety and Health Administration.
Powder chest means a substantial, nonconductive portable container equipped with a lid and used at blasting sites for explosives other than blasting agents.
Primer means a unit, package, or cartridge of explosives used to initiate other explosives or blasting agents, and which contains a detonator.
Reverse-current protection means a method or device used on direct-current circuits or equipment to prevent the flow of current in a reverse direction.
Rock burst means a sudden and violent failure of overstressed rock resulting in the instantaneous release of large amounts of accumulated energy. Rock burst does not include a burst resulting from pressurized mine gases.
Rock fixture means any tensioned or nontensioned device or material inserted into the ground to strengthen or support the ground.
Roll protection means a framework, safety canopy or similar protection for the operator when equipment overturns.
Safety can means an approved container, of not over 5 gallons capacity, having a spring-closing lid and spout cover.
Safety fuse means a flexible cord containing an internal burning medium by which fire is conveyed at a continuous and uniform rate for the purpose of firing blasting caps or a black powder charge.
Safety switch means a sectionalizing switch that also provides shunt protection in blasting circuits between the blasting switch and the shot area.
Scaling means removal of insecure material from a face or highwall.
Secondary safety connection means a second connection between a conveyance and rope, intended to prevent the conveyance from running away or falling in the event the primary connection fails.
Shaft means a vertical or inclined shaft, a slope, incline, or winze.
Short circuit means an abnormal connection of relatively low resistance, whether made accidentally or intentionally, between two points of difference potential in a circuit.
Slurry (as applied to blasting). See “Water gel.”
Storage facility means the entire class of structures used to store explosive materials. A “storage facility” used to store blasting agents corresponds to a BATF Type 4 or 5 storage facility.
Storage tank means a container exceeding 60 gallons in capacity used for the storage of flammable or combustible liquids.
Stray current means that portion of a total electric current that flows through paths other than the intended circuit.
Substantial construction means construction of such strength, material, and workmanship that the object will withstand all reasonable shock, wear, and usage to which it will be subjected.
Suitable means that which fits, and has the qualities or qualifications to meet a given purpose, occasion, condition, function, or circumstance.
Travelway means a passage, walk or way regularly used and designated for persons to go from one place to another.
Water gel or Slurry (as applied to blasting) means an explosive or blasting agent containing substantial portions of water.
Wet drilling means the continuous application of water through the central hole of hollow drill steel to the bottom of the drill hole.
Working level (WL) means any combination of the short-lived radon daughters in one liter of air that will result in ultimate emission of 1.3 × 105 MeV (million electron volts) of potential alpha energy, and exposure to these radon daughters over a period of time is expressed in terms of “working level months” (WLM). Inhalation of air containing a radon daughter concentration of 1 WL for 173 hours results in an exposure of 1 WLM.”
Working place means any place in or about a mine where work is being performed.
[69 FR , June 29, , as amended at 80 FR , Sept. 2, ]
Circuits shall be protected against excessive overloads by fuses or circuit breakers of the correct type and capacity.
Electric equipment and circuits shall be provided with switches or other controls. Such switches or controls shall be of approved design and construction and shall be properly installed.
Individual overload protection or short circuit protection shall be provided for the trailing cables of mobile equipment.
Electrical conductors shall be of a sufficient size and current-carrying capacity to ensure that a rise in temperature resulting from normal operations will not damage the insulating materials. Electrical conductors exposed to mechanical damage shall be protected.
Mobile equipment shall not run over power conductors, nor shall loads be dragged over power conductors, unless the conductors are properly bridged or protected.
Distribution boxes shall be provided with a disconnecting device for each branch circuit. Such disconnecting devices shall be equipped or designed in such a manner that it can be determined by visual observation when such a device is open and that the circuit is deenergized, and the distribution box shall be labeled to show which circuit each device controls.
Trailing cable and power-cable connections to junction boxes shall not be made or broken under load.
Power wires and cables shall be insulated adequately where they pass into or out of electrical compartments. Cables shall enter metal frames of motors, splice boxes, and electrical compartments only through proper fittings. When insulated wires, other than cables, pass through metal frames, the holes shall be substantially bushed with insulated bushings.
and low-potential signal wire shall be protected, by isolation or suitable insulation, or both, from contacting energized power conductors or any other power source.
High-potential electrical conductors shall be covered, insulated, or placed to prevent contact with low potential conductors.
The potential on bare signal wires accessible to contact by persons shall not exceed 48 volts.
Permanent splices and repairs made in power cables, including the ground conductor where provided, shall be—
(a) Mechanically strong with electrical conductivity as near as possible to that of the original;
(b) Insulated to a degree at least equal to that of the original, and sealed to exclude moisture; and,
(c) Provided with damage protection as near as possible to that of the original, including good bonding to the outer jacket.
Power cables energized to potentials in excess of 150 volts, phase-to-ground, shall not be moved with equipment unless sleds or slings, insulated from such equipment, are used. When such energized cables are moved manually, insulated hooks, tongs, ropes, or slings shall be used unless suitable protection for persons is provided by other means. This does not prohibit pulling or dragging of cable by the equipment it powers when the cable is physically attached to the equipment by suitable mechanical devices, and the cable is insulated from the equipment in conformance with other standards in this part.
Electrically powered equipment shall be deenergized before mechanical work is done on such equipment. Power switches shall be locked out or other measures taken which shall prevent the equipment from being energized without the knowledge of the individuals working on it. Suitable warning notices shall be posted at the power switch and signed by the individuals who are to do the work. Such locks or preventive devices shall be removed only by the persons who installed them or by authorized personnel.
Power circuits shall be deenergized before work is done on such circuits unless hot-line tools are used. Suitable warning signs shall be posted by the individuals who are to do the work. Switches shall be locked out or other measures taken which shall prevent the power circuits from being energized without the knowledge of the individuals working on them. Such locks, signs, or preventive devices shall be removed only by the person who installed them or by authorized personnel.
Principal power switches shall be labeled to show which units they control, unless identification can be made readily by location.
Where access is necessary, suitable clearance shall be provided at stationary electrical equipment or switchgear.
Dry wooden platforms, insulating mats, or other electrically-nonconductive material shall be kept in place at all switchboards and power-control switches where shock hazards exist. However, metal plates on which a person normally would stand and which are kept at the same potential as the grounded, metal, non-current-carrying parts of the power switches to be operated may be used.
Suitable danger signs shall be posted at all major electrical installations.
Areas containing major electrical installations shall be entered only by authorized persons.
Electrical connections and resistor grids that are difficult or impractical to insulate shall be guarded, unless protection is provided by location.
All metal enclosing or encasing electrical circuits shall be grounded or provided with equivalent protection. This requirement does not apply to battery-operated equipment.
Metal fencing and metal buildings enclosing transformers and switchgear shall be grounded.
Frame grounding or equivalent protection shall be provided for mobile equipment powered through trailing cables.
Continuity and resistance of grounding systems shall be tested immediately after installation, repair, and modification; and annually thereafter. A record of the resistance measured during the most recent test shall be made available on a request by the Secretary or his duly authorized representative.
When a potentially dangerous condition is found it shall be corrected before equipment or wiring is energized.
Inspection and cover plates on electrical equipment and junction boxes shall be kept in place at all times except during testing or repairs.
Hand-held electric tools shall not be operated at high potential voltages.
Portable extension lights, and other lights that by their location present a shock or burn hazard, shall be guarded.
Lamp sockets shall be of a weatherproof type where they are exposed to weather or wet conditions that may interfere with illumination or create a shock hazard.
Fuses shall not be removed or replaced by hand in an energized circuit, and they shall not otherwise be removed or replaced in an energized circuit unless equipment and techniques especially designed to prevent electrical shock are provided and used for such purpose.
Fuse tongs or hotline tools, shall be used when fuses are removed or replaced in high-potential circuits.
Trailing cables shall be attached to machines in a suitable manner to protect the cable from damage and to prevent strain on the electrical connections.
Surplus trailing cables to shovels, cranes and similar equipment shall be—
(a) Stored in cable boats;
(b) Stored on reels mounted on the equipment; or
(c) Otherwise protected from mechanical damage.
Operating controls shall be installed so that they can be operated without danger of contact with energized conductors.
Switches and starting boxes shall be of safe design and capacity.
Both rails shall be bonded or welded at every joint and rails shall be crossbonded at least every 200 feet if the track serves as the return trolley circuit. When rails are moved, replaced, or broken bonds are discovered, they shall be rebonded within three working shifts.
Overhead high-potential powerlines shall be installed as specified by the National Electrical Code.
Guy wires of poles supporting high-voltage transmission lines shall meet the requirements for grounding or insulator protection of the National Electrical Safety Code, part 2, entitled “Safety Rules for the Installation and Maintenance of Electric Supply and Communication Lines” (also referred to as National Bureau of Standards Handbook 81, Nov. 1, ), and Supplement 2 thereof issued March , which are hereby incorporated by reference and made a part hereof. These publications and documents may be obtained from the National Institute of Science and Technology, 100 Bureau Drive, Stop , Gaithersburg, MD -. : 301-975- (not a toll free number); http://ts.nist.gov/nvl; or from the Government Printing Office, Information Dissemination (Superintendent of Documents), P.O. Box , Pittsburgh, PA -; : 866-512- (toll free) or 202-512-; http://bookstore.gpo.gov, or may be examined in any Metal and Nonmetal Mine Safety and Health District Office of the Mine Safety and Health Administration.
[53 FR , Aug. 25, , as amended at 60 FR , July 11, ; 71 FR , Apr. 3, ]
Telegraph, , or signal wires shall not be installed on the same crossarm with power conductors. When carried on poles supporting powerlines, they shall be installed as specified by the National Electrical Code.
Trolley wires shall be installed at least seven feet above rails where height permits, and aligned and supported to suitably control sway and sag.
Ground wires for lighting circuits powered from trolley wires shall be connected securely to the ground return circuit.
When a manually operated hoist is used, a qualified hoistman shall remain within hearing of the or signal device at all times while any person is underground.
When automatic hoisting is used, a competent operator of the hoist shall be readily available at or near the hoisting device while any person is underground.
No person shall operate a hoist unless within the preceding 12 months he has had a medical examination by a qualified, licensed physician who shall certify his fitness to perform this duty. Such certification shall be available at the mine.
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Only experienced hoistmen shall operate the hoist except in cases of emergency and in the training of new hoistmen.
The safe speed for hoisting persons shall be determined for each shaft, and this speed shall not be exceeded. Persons shall not be hoisted at a speed faster than 2,500 feet per minute, except in an emergency.
Maximum normal operating acceleration and deceleration shall not exceed 6 feet per second per second. During emergency braking, the deceleration shall not exceed 16 feet per second per second.
Only authorized persons shall be in hoist rooms.
Conveyances shall not be lowered by the brakes alone except during emergencies.
In shafts inclined over 45 degrees, the operator shall determine and post in the conveyance or at each shaft station the maximum number of persons permitted to ride in a hoisting conveyance at any one time. Each person shall be provided a minimum of 1.5 square feet of floor space.
During shift changes, an authorized person shall be in charge of each trip in which persons are hoisted.
Persons shall enter, ride, and leave conveyances in an orderly manner.
Persons shall not enter or leave conveyances which are in motion or after a signal to move the conveyance has been given to the hoistman.
Cage doors or gates shall be closed while persons are being hoisted; they shall not be opened until the cage has come to a stop.
Persons shall not ride in skips or buckets with muck, supplies, materials, or tools other than small hand tools.
When combinations of cages and skips are used in the same compartment, the cages shall be enclosed to protect personnel from flying material and the hoist speed reduced to man-speed as defined in standard 57., but not to exceed 1,000 feet per minute. Muck shall not be hoisted with personnel during shift changes.
Rock or supplies shall not be hoisted in the same shaft as persons during shift changes, unless the compartments and dumping bins are partitioned to prevent spillage into the cage compartment.
Persons shall not ride the bail, rim, bonnet, or crosshead of any shaft conveyance except when necessary for inspection and maintenance, and then only when suitable protection for persons is provided.
Open hooks shall not be used to hoist buckets or other conveyances.
When persons are hoisted in buckets, speeds shall not exceed 500 feet per minute and shall not exceed 200 feet per minute when within 100 feet of the intended station.
Buckets shall be stopped about 15 feet from the shaft bottom to await a signal from one of the crew on the bottom for further lowering.
All buckets shall be stopped after being raised about three feet above the shaft bottom. A bucket shall be stabilized before a hoisting signal is given to continue hoisting the bucket to the crosshead. After a hoisting signal is given, hoisting to the crosshead shall be at a minimum speed. The signaling device shall be attended constantly until a bucket reaches the guides. When persons are hoisted, the signaling devices shall be attended until the crosshead has been engaged.
Where mine cars are hoisted by cage or skip, means for blocking cars shall be provided at all landings and also on the cage.
When tools, timbers, or other materials are being lowered or raised in a shaft by means of a bucket, skip, or cage, they shall be secured or so placed that they will not strike the sides of the shaft.
When conveyances controlled by a hoist operator are not in use, they shall be released and the conveyances shall be raised or lowered a suitable distance to prevent persons from boarding or loading the conveyances.
A manually operated device shall be installed on each electric hoist that will allow the conveyance or counterbalance to be removed from an overtravel position. Such device shall not release the brake, or brakes, holding the overtravelled conveyance or counterbalance until sufficient drive motor torque has been developed to assure movement of the conveyance or counterbalance in the correct direction only.
All mines shall be ventilated mechanically.
(a) Main fans shall be—
(1) Installed on the surface in noncombustible housings provided with noncombustible air ducts;
(2) Except in Subcategory I-A mines, provided with an automatic signal device to give an alarm when the fan stops. The signal device shall be located so that it can be seen or heard by a person designated by the mine operator.
(b) Fan installations shall be—
(1) Offset so that the fan and its associated components are not in direct line with possible explosive forces;
(2) Equipped with explosion-doors, a weak-wall, or other equivalent devices located to relieve the pressure that would be created by an explosion underground. The area of the doors or weak-wall shall be at least equivalent to the average cross-sectional area of the airway.
(c)
(1) All main fan-related electrical equipment and cables located within or exposed to the forward or reverse airstream shall be approved by MSHA under the appliable requirements of 30 CFR part 18;
(2) Drive belts and nonmetallic fan blades shall be constructed of static-conducting material; and
(3) Aluminum alloy fan blades shall not contain more than 0.5 percent magnesium. [Paragraph (c)(3) of this section does not apply to Subcategory I-C mines].
(d) When an internal combustion engine is used to power a main fan or as standby power, the engine shall be—
(1) Installed in a noncombustible housing;
(2) Protected from a possible fuel supply fire or explosion; and
(3) Located out of direct line with the forward and reverse airstream provided by the fan. Engine exhaust gases shall be vented to the atmosphere so that exhaust cannot contaminate mine intake air.
(e) For Subcategory I-A mines only: Main exhaust fans shall be equipped with methane monitors to give an alarm when methane in the return air reaches 0.5 percent. The alarm shall be located so that it can be seen or heard by a person designated by the mine operator.
[52 FR , July 1, , as amended at 52 FR , Oct. 27, ]
Main fans shall be operated continuously while ore production is in progress.
Main fans shall be—
(a) Provided with a pressure-recording system; and
(b) Inspected daily while operating if persons are underground. Certification of inspections shall be made by signature and date. Certifications and pressure recordings shall be retained for at least one year and made available to an authorized representative of the Secretary.
[52 FR , July 1, , as amended at 52 FR , Oct. 27, ; 60 FR , June 29, ]
In mines ventilated by multiple main fans, each main fan installation shall be equipped with noncombustible doors. Such doors shall automatically close to prevent air reversal through the fan. The doors shall be located so that they are not in direct line with explosive forces which could come out of the mine.
(a) When there has been a main ventilation failure, such as stoppage of main fans or failure of other components of the main ventilation system, tests for methane shall be conducted in affected active workings until normal air flow has resumed.
(b) If a total failure of ventilation occurs while all persons are out of the mine and the failure lasts for more than 30 minutes, only competent persons shall be allowed underground to examine the mine or to make necessary ventilation changes. Other persons may reenter the mine after the main fans have been operational for at least 30 minutes, or after the mine atmosphere has been tested and contains less than 1.0 percent methane. Persons other than examiners shall not reenter a Subcategory II-A mine until the methane level is less than 0.5 percent.
(a) Booster fans shall be approved by MSHA under the applicable requirements of 30 CFR part 18, and be—
(1) Provided with an automatic signal device located so that it can be seen or heard by a person designated by the mine operator to give an alarm when the fan stops or when methane reaches the following levels:
(i) 1.0 percent at the fan in Subcategory I-A, Category III, and Subcategory V-A mines; and
(ii) 0.5 percent at the fan in Subcategory II-A mines.
(2) Equipped with a device that automatically deenergizes power in affected workings should the fan stop; and
(3) Equipped with starting and stopping controls located at the fan and at another accessible remote location.
(b) Booster fan installations, except for booster fans installed in ducts, shall be—
(1) Provided with doors which open automatically when all fans in the installation stop; and
(2) Provided with an air lock when passage through the fan bulkhead is necessary.
(a) Auxiliary fans, except fans used in shops and other areas which have been so designed that methane cannot enter the airway, shall be approved by MSHA under the applicable requirements of 30 CFR part 18, and be operated so that recirculation is minimized. Auxiliary fans shall not be used to ventilate work places during the interruption of normal mine ventilation.
(b) Tests for methane shall be made at auxiliary fans before they are started.
Electric auxiliary fans shall be approved by MSHA under the applicable requirements of 30 CFR part 18. Tests for methane shall be made at electric auxiliary fans before they are started. Such fans shall not be operated when air passing over or through them contains 0.5 percent or more methane.
Filters or separators shall be installed on air-lift fan systems to prevent explosive concentrations of dust from passing through the fan.
The average air velocity in the last open crosscut in pairs or sets of developing entries, or through other ventilation openings nearest the face, shall be at least 40 feet per minute. The velocity of air ventilating each face at a work place shall be at least 20 feet per minute.
Air flow across each working face shall be sufficient to carry away any accumulation of methane, smoke, fumes, and dust.
The quantity of air coursed through the last open crosscut in pairs or sets of entries, or through other ventilation openings nearest the face, shall be at least 6,000 cubic feet per minute, or 9,000 cubic feet per minute in longwall and continuous miner sections. The quantity of air across each face at a work place shall be at least 2,000 cubic feet per minute.
(a) Changes in ventilation which affect the main air current or any split thereof and which adversely affect the safety of persons in the mine shall be made only when the mine is idle.
(b) Only persons engaged in making such ventilation changes shall be permitted in the mine during changes.
(c) Power shall be deenergized in affected areas prior to making ventilation changes, except power to monitoring equipment determined by MSHA to be intrinsically safe under 30 CFR part 18. Power shall not be restored until the results of the change have been determined and a competent person has examined affected working places for methane.
Main intake and return air currents shall be coursed through separate mine openings and shall be separated throughout the mine, except—
(a) Where multiple shafts are used for ventilation and a single shaft contains a curtain wall or partition for separation of air currents. Such wall or partition shall be constructed of reinforced concrete or other noncombustible equivalent, and provided with pressure-relief devices.
(b) During development of openings to the surface—
(1) Ventilation tubing approved by MSHA in accordance with 30 CFR part 7 or previously issued a BC or VT acceptance number by the MSHA Approval and Certification Center may be used for separation of main air currents in the same opening. Flexible ventilation tubing shall not exceed 250 feet in length.
(2) Only development related to making a primary ventilation connection may be performed beyond 250 feet of the shaft.
[52 FR , July 1, , as amended at 54 FR , July 20, ]
The main intake and return air currents in single shafts shall be separated by ventilation tubing, curtain walls, or partitions. Ventilation tubing shall be constructed of noncombustible material. Curtain walls or partitions shall be constructed of reinforced concrete or other noncombustible equivalent, and provided with pressure-relief devices.
All seals, and those stoppings that separate main intake from main return airways, shall be of substantial construction and constructed of noncombustible materials, except that stoppings constructed of brattice materials may be used in face areas.
(a) All seals, and those stoppings that separate main intake from main return airways, shall be of substantial construction, except that stoppings constructed of brattice materials may be used in face areas.
(b) Exposed surfaces on the intake side of stoppings constructed of combustible materials or foam-type blocks shall be coated with at least one inch of construction plaster containing perlite and gypsum; at least one inch of expanded vermiculite, Portland cement and limestone; or other coatings with equivalent fire resistance. Stoppings constructed to phenolic foam blocks at least 12 inches thick need not be coated for fire resistance. All foam-type blocks used for stopping construction shall be solid.
(c) Exposed surfaces on the fresh air side of seals constructed of combustible materials shall be coated with at least one inch of construction plaster containing perlite and gypsum; at least one inch of expanded vermiculite, Portland cement and limestone; or other coatings with equivalent fire resistance. Foam-type blocks shall not be used for seals.
(a) Exposed surfaces on the intake side of stoppings constructed of combustible materials, except brattice, shall be coated with at least one inch of construction plaster containing perlite and gypsum; at least one inch of expanded vermiculite, Portland cement and limestone; or other coatings with equivalent fire resistance.
(b) Seals shall be of substantial construction. Exposed surfaces on the fresh air side of seals constructed of combustible materials shall be coated with at least one inch of construction plaster containing perlite and gypsum; at least one inch of expanded vermiculite, Portland cement and limestone; or other coatings with equivalent fire resistance. Foam-type blocks shall not be used for seals.
Air that has passed by or through unsealed abandoned or unsealed inactive areas and contains 0.25 percent or more methane shall—
(a) Be coursed directly to a return airway;
(b) Be tested daily for methane by a competent person; and
(c) Not be used to ventilate work places.
Overcasts and undercasts shall be—
(a) Of substantial construction;
(b)
(1) Constructed of noncombustible materials; or
(2) Where constructed of combustible materials, the outside surfaces shall be coated with at least one inch of construction plaster containing perlite and gypsum; at least one inch of expanded vermiculite, Portland cement and limestone; or other coatings with equivalent fire resistance;
(c) Kept clear of obstructions.
Brattice cloth and ventilation tubing shall be approved by MSHA in accordance with 30 CFR part 7, or shall bear a BC or VT acceptance number issued by the MSHA Approval and Certification Center.
[54 FR , July 20, ]
A means of ventilating faces shall be provided before workings are abandoned in unsealed areas, unless crosscuts are provided within 30 feet of the face.
Battery charging stations, compressor stations, pump stations, and transformer stations shall be installed in intake air at locations which are sufficiently ventilated to prevent the accumulation of methane.
Battery charging stations, compressor stations, and electrical substations shall not be installed underground or within 50 feet of a mine opening.
Tests for methane shall be conducted in the mine atmosphere by a competent person—
(a) At least once each shift prior to starting work in each face and raise; and
(b) Upon initial release of gas into the mine atmosphere from boreholes.
(a) Methane monitoring devices and portable, battery-powered, self-contained devices used for measuring methane, other gases, and contaminants in mine air shall be approved by MSHA under the applicable requirements of 30 CFR parts 18, 21, 22, 23, 27, and 29. Such devices shall be maintained in accordance with manufacturers' instructions, or an equivalent maintenance and calibration procedure.
(b)
(1) Flame safety lamps shall not be used to test for methane except as supplementary devices.
(2) Flame safety lamps shall not be used in Subcategory I-C mines.
(c)
(1) If electrically powered, remote sensing devices are used, that portion of the instrument located in return air or other places where combustible gases may be present shall be approved by MSHA under the applicable requirements of 30 CFR parts 18, 22, 23, 27, and 29.
(2) If air samples are delivered to remote analytical devices through sampling tubes, such tubes shall be provided with in-line flame arrestors. Pumping equipment and analytical instruments shall be located in intake air.
(a) Preshift examinations shall be conducted within three hours prior to the start of the shift for which the examination is being made.
(b) Prior to the beginning of a shift following an idle shift, a competent person shall test the mine atmosphere for methane at all work places before persons other than examiners enter the mine.
(c) When one shift immediately follows another, a competent person shall test the mine atmosphere at each active working face for methane before work is started on that shift.
(d) A competent person shall test the mine atmosphere at each face blasted before work is started.
(e) Except in Subcategory I-C or Category III mines, vehicles used for transportation when examining the mine shall be approved by MSHA under the applicable requirements of 30 CFR parts 18 through 36.
[52 FR , July 1, , as amended at 53 FR , Mar. 24, ]
(a) The mine atmosphere shall be tested for methane and carbon monoxide at least once every seven days by a competent person or an atmospheric monitoring system, or a combination of the two. Such testing shall be done at the following locations:
(1) The return of each split where it enters the main return;
(2) Adjacent to retreat areas, if accessible;
(3) At least one seal of each sealed area, if accessible;
(4) Main returns;
(5) At least one entry of each intake and return;
(6) Idle workings; and
(7) Return air from unsealed abandoned workings.
(b) The volume of air (velocity in Subcategory I-A mines) shall be measured at least once every seven days by a competent person. Such measurement shall be done at the following locations:
(1) Entering main intakes;
(2) Leaving main returns;
(3) Entering each main split;
(4) Returning from each main split; and
(5) In the last open crosscuts or other ventilation openings nearest the active faces where the air enters the return.
(c) Where such examinations disclose hazardous conditions, affected persons shall be informed and corrective action shall be taken.
(d) Certification of examinations shall be made by signature and date. Certifications shall be retained for at least one year and made available to authorized representatives of the Secretary.
[52 FR , July 1, , as amended at 52 FR , Oct. 27, ]
(a) The mine atmosphere shall be tested for methane at least once every seven days by a competent person or an atmospheric monitoring system, or a combination of the two. Such testing shall be done at the following locations:
(1) Active mining faces and benches;
(2) Main returns;
(3) Returns from idle workings;
(4) Returns from abandoned workings; and
(5) Seals.
(b) Where such examinations disclose hazardous conditions, affected persons shall be informed and corrective action shall be taken.
(c) Certification of examinations shall be made by signature and date. Certifications shall be kept for at least one year and made available to authorized representatives of the Secretary.
[52 FR , July 1, , as amended at 52 FR , Oct. 27, ; 60 FR , June 29, ]
If methane reaches 0.25 percent in the mine atmosphere, changes shall be made to improve ventilation, and MSHA shall be notified immediately.
If methane reaches 0.5 percent in the mine atmosphere, ventilation changes shall be made to reduce the level of methane. Until methane is reduced to less than 0.5 percent, electrical power shall be deenergized in affected areas, except power to monitoring equipment determined by MSHA to be intrinsically safe under 30 CFR part 18. Diesel equipment shall be shut off or immediately removed from the area and no other work shall be permitted in affected areas.
[52 FR , July 1, ; 52 FR , July 24, ]
If methane reaches 0.5 percent in the mine atmosphere, ventilation changes shall be made to reduce the level of methane. Until methane is reduced to less than 0.5 percent, no other work shall be permitted in affected areas.
[52 FR , July 1, ; 52 FR , July 24, ]
(a) If methane reaches 1.0 percent in the mine atmosphere, ventilation changes shall be made to reduce the methane. Until such changes are achieved—
(1) All persons other than competent persons necessary to make the ventilation changes shall be withdrawn from affected areas;
(2) Electrical power shall be deenergized in affected areas, except power to monitoring equipment determined by MSHA to be intrinsically safe under 30 CFR part 18; and
(3) Diesel equipment shall be shut off or immediately removed from the area.
(b) If methane reaches 1.0 percent at a main exhaust fan, electrical power underground shall be deenergized, except power to monitoring equipment determined by MSHA to be intrinsically safe under 30 CFR part 18, and all persons shall be withdrawn from the mine.
(c) If methane reaches 1.0 percent at a work place and there has been a failure of the main ventilation system, all persons shall be withdrawn from the mine.
[52 FR , July 1, , as amended at 53 FR , Mar. 24, ]
(a) If methane reaches 1.0 percent in the mine atmosphere, all persons other than competent persons necessary to make ventilation changes shall be withdrawn from affected areas until methane is reduced to less than 0.5 percent.
(b) If methane reaches 1.0 percent at a work place and there has been a failure of the main ventilation system, all persons shall be withdrawn from the mine.
If methane reaches 1.0 percent in the mine atmosphere, all persons other than competent persons necessary to make ventilation changes shall be withdrawn from affected areas until methane is reduced to less than 0.5 percent.
If methane reaches 2.0 percent in bleeder systems at the point where a bleeder split enters a main return split, mining shall not be permitted on ventilation splits affected by the bleeder system. If methane has not been reduced to less than 2.0 percent within 30 minutes, or if methane levels reach 2.5 percent, all persons other than competent persons necessary to take corrective action shall be withdrawn from affected areas.
If methane reaches 2.0 percent in the mine atmosphere, all persons other than competent persons necessary to make ventilation changes shall be withdrawn from the mine until methane is reduced to less than 0.5 percent.
If methane reaches 2.0 percent in the mine atmosphere, all persons other than competent persons necessary to make ventilation changes shall be withdrawn from the mine until methane is reduced to less than 0.5 percent. MSHA shall be notified immediately.
[52 FR , July 1, , as amended at 52 FR , Oct. 27, ; 60 FR , June 29, ]
If methane reaches 2.0 percent in the mine atmosphere, all persons other than competent persons necessary to make ventilation changes shall be withdrawn from affected areas until methane is reduced to less than 1.0 percent.
[52 FR , July 1, ; 52 FR , July 24, ]
(a) Boreholes shall be drilled at least 25 feet in advance of a face whenever the work place is within—
(1) 50 feet of a surveyed abandoned mine or abandoned workings which cannot be inspected; or
(2) 200 feet of an unsurveyed abandoned mine or abandoned workings which cannot be inspected.
(b) Boreholes shall be drilled in such a manner to insure that the advancing face will not accidently break into an abandoned mine or abandoned working.
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