{"data":{"id":"us/30-cfr-57.2","jurisdiction":"us","citation":"30 CFR 57.2","heading":"Definitions.","body":"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:\nAbandoned areas means areas in which work has been completed, no further work is planned, and travel is not permitted.\nAbandoned mine means all work has stopped on the mine premises and an office with a responsible person in charge is no longer maintained at the mine.\nAbandoned workings means deserted mine areas in which further work is not intended.\nActive workings means areas at, in, or around a mine or plant where men work or travel.\nAmerican 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.\nApproved means tested and accepted for a specific purpose by a nationally recognized agency.\nAttended 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.\nAuthorized 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.\nAuxilary fan means a fan used to deliver air to a working place off the main airstream; generally used with ventilation tubing.\nBarricaded means obstructed to prevent the passage of persons, vehicles, or flying materials.\nBarrier means a material object, or objects that separates, keeps apart, or demarcates in a conspicuous manner such as cones, a warning sign, or tape.\nBerm 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.\nBlast 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:\n(1) Geology or material to be blasted.\n(2) Blast pattern.\n(3) Burden, depth, diameter, and angle of the holes.\n(4) Blasting experience of the mine.\n(5) Delay system, powder factor, and pounds per delay.\n(6) Type and amount of explosive material.\n(7) Type and amount of stemming.\nBlast 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.\nBlasting agent means any substance classified as a blasting agent by the Department of Transportation in 49 CFR 173.114(a) (44 FR 31182, May 31, 1979) 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 20402.\nBlasting area means the area near blasting operations in which concussion or flying material can reasonably be expected to cause injury.\nBlasting cap means a detonator which is initiated by a safety fuse.\nBlasting circuit means the electrical circuit used to fire one or more electric blasting caps.\nBlasting switch means a switch used to connect a power source to a blasting circuit.\nBlowout means a sudden, violent, release of gas or liquid due to the reservoir pressure in a petroleum mine.\nBooster means any unit of explosive or blasting agent used for the purpose of perpetuating or intensifying an initial detonation.\nBooster 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.\nCapped fuse means a length of safety fuse to which a blasting cap has been attached.\nCapped primer means a package or cartridge of explosives which is specifically designed to transmit detonation to other explosives and which contains a detonator.\nCircuit 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.\nCombustible means capable of being ignited and consumed by fire.\nCombustible 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.\nCompany official means a member of the company supervisory or technical staff.\nCompetent person means a person having abilities and experience that fully qualify him to perform the duty to which he is assigned.\nConductor means a material, usually in the form of a wire, cable, or bus bar, capable of carrying an electric current.\nDelay connector means a nonelectric short interval delay device for use in delaying blasts which are initiated by detonating cord.\nDetonating cord means a flexible cord containing a solid core of high explosives.\nDetonator 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.\nDistribution 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.\nElectric blasting cap means a detonator designed for and capable of being initiated by means of an electric current.\nElectrical grounding means to connect with the ground to make the earth part of the circuit.\nEmployee means a person who works for wages or salary in the service of an employer.\nEmployer means a person or organization which hires one or more persons to work for wages or salary.\nEmulsion means an explosive material containing substantial amounts of oxidizers dissolved in water droplets, surrounded by an immiscible fuel.\nEscapeway means a passageway by which persons may leave a mine.\nExplosive 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 20402.\nFace or bank means that part of any mine where excavating is progressing or was last done.\nFire 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.\nFlame 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.\nFlammable means capable of being easily ignited and of burning rapidly.\nFlammable gas means a gas that will burn in the normal concentrations of oxygen in the air.\nFlammable 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.\nFlash 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.\nGeological 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.\nHighway means any public street, public alley or public road.\nHigh potential means more than 650 volts.\nHoist 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.\nIgniter 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.\nInsulated 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.\nInsulation means a dielectric substance offering a high resistance to the passage of current and to a disruptive discharge through the substance.\nLaminated 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 1993), and the “Generic Loading Guide for the IME-22 Container” (October 1993). The IME is located at 1120 19th Street NW., Suite 310, Washington, DC 20036-3605; 202-429-9280; 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, 200 Constitution Avenue NW, Washington, DC 20210; 202-693-9440; 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 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.\nLay means the distance parallel to the axis of the rope in which a strand makes one complete turn about the axis of the rope.\nLoading means placing explosive material either in a blasthole or against the material to be blasted.\nLow potential means 650 volts or less.\nMagazine means a facility for the storage of explosives, blasting agents, or detonators.\nMain fan means a fan that controls the entire airflow of the mine, or the airflow of one of the major air circuits.\nMajor electrical installation means an assemblage of stationary electrical equipment for the generation, transmission, distribution, or conversion of electrical power.\nMantrip means a trip on which persons are transported to and from a work area.\nMill includes any ore mill, sampling works, concentrator, and any crushing, grinding, or screening plant used at, and in connection with, an excavation or mine.\nMine 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.\nMine opening means any opening or entrance from the surface into a mine.\nMisfire means the complete or partial failure of a blasting charge to explode as planned.\nMobile equipment means wheeled, skid-mounted, track-mounted, or rail-mounted equipment capable of moving or being moved.\nMultipurpose 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.\nNoncombustible 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.\nNon-electric delay blasting cap means a detonator with an integral delay element and capable of being initiated by miniaturized detonating cord.\nOutburst means the sudden, violent release of solids and high-pressure occluded gases, including methane in a domal salt mine.\nOverburden means material of any nature, consolidated or unconsolidated, that overlies a deposit of useful materials or ores that are to be mined.\nOverload means that current which will cause an excessive or dangerous temperature in the conductor or conductor insulation.\nPermissible 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.\nPotable 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, 1977. 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, 1976. 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.\nPowder chest means a substantial, nonconductive portable container equipped with a lid and used at blasting sites for explosives other than blasting agents.\nPrimer means a unit, package, or cartridge of explosives used to initiate other explosives or blasting agents, and which contains a detonator.\nReverse-current protection means a method or device used on direct-current circuits or equipment to prevent the flow of current in a reverse direction.\nRock 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.\nRock fixture means any tensioned or nontensioned device or material inserted into the ground to strengthen or support the ground.\nRoll protection means a framework, safety canopy or similar protection for the operator when equipment overturns.\nSafety can means an approved container, of not over 5 gallons capacity, having a spring-closing lid and spout cover.\nSafety 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.\nSafety switch means a sectionalizing switch that also provides shunt protection in blasting circuits between the blasting switch and the shot area.\nScaling means removal of insecure material from a face or highwall.\nSecondary 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.\nShaft means a vertical or inclined shaft, a slope, incline, or winze.\nShort circuit means an abnormal connection of relatively low resistance, whether made accidentally or intentionally, between two points of difference potential in a circuit.\nSlurry (as applied to blasting). See “Water gel.”\nStorage 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.\nStorage tank means a container exceeding 60 gallons in capacity used for the storage of flammable or combustible liquids.\nStray current means that portion of a total electric current that flows through paths other than the intended circuit.\nSubstantial 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.\nSuitable means that which fits, and has the qualities or qualifications to meet a given purpose, occasion, condition, function, or circumstance.\nTravelway means a passage, walk or way regularly used and designated for persons to go from one place to another.\nWater gel or Slurry (as applied to blasting) means an explosive or blasting agent containing substantial portions of water.\nWet drilling means the continuous application of water through the central hole of hollow drill steel to the bottom of the drill hole.\nWorking 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 × 10 5 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.”\nWorking place means any place in or about a mine where work is being performed.","path":["Title 30—Mineral Resources","CHAPTER I—MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR","SUBCHAPTER K—METAL AND NONMETAL MINE SAFETY AND HEALTH","PART 57—SAFETY AND HEALTH STANDARDS—UNDERGROUND METAL AND NONMETAL MINES","Subpart A—General"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-30.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:25:24Z","sha256":"9d9bd857bd3170f2bcb08d657f226ba1a396e3f72bed1c833445aa7e4922db18","source_id":"us-cfr","stale":true,"prev":"us/30-cfr-57.1","next":"us/30-cfr-57.1000"},"notice":"GroundRules: Original legal text. Not legal advice."}