(a)MSHA means the United States Department of Labor, Mine Safety and
(b)Applicant means an individual, partnership, company, corporation,
association, or other organization that designs, manufactures, or assembles
and that seeks certification or preliminary testing of a methane-monitoring
system or component.
(c)Methane-monitoring system means a complete assembly of one or
more methane detectors and all other components required for measuring and
signalling the presence of methane in the atmosphere of a mine, tunnel, or
other underground workings, and shall include a power-shutoff component.
(d)Methane detector means a component for a methane-monitoring
system that functions in a gassy mine, tunnel, or other underground workings
to sample the atmosphere continuously and responds to the presence of
(e)Power-shutoff component means a component of a methane-monitoring
system, such as a relay, switch, or switching mechanism, that will cause a
control circuit to deenergize a machine, equipment, or power circuit when
actuated by the methane detector.
(f)Flammable mixture means a mixture of a gas, such as methane,
natural gas, or similar hydrocarbon gas with normal air, that can be
(g)Gassy mine or tunnel means a mine, tunnel, or other underground
workings in which a flammable mixture has been ignited, or has been found
with a permissible flame safety lamp, or has been determined by air analysis
to contain 0.25 percent or more (by volume) of methane in any open workings
when tested at a point not less than 12 inches from the roof, face, or
(h)Letter of certification means a formal document issued by MSHA
stating that a methane-monitoring system or subassembly or component
(1) Has met the requirements of this part, and
(2) Is certified for incorporation in or with permissible or approved
equipment that is used in gassy mines and tunnels.
(i)Component means a part of a methane-monitoring system that is
essential to its operation as a certified methane-monitoring system.
(j)Explosion-proof means that a component or group of components
(subassembly) is so constructed and protected by an enclosure with or without
a flame arrester(s) that, if a flammable mixture of gas is ignited within the
enclosure, it will withstand the resultant pressure without damage to the
enclosure and/or flame arrester(s). Also the enclosure and/or flame
arrester(s) shall prevent the discharge of flame from within either the
enclosure or the flame arrester, or the ignition of any flammable mixture
that surrounds the enclosure and/or flame arrester.1
1 Explosion-proof components or subassemblies shall be constructed in
accordance with the requirements of Part 18 of this
(k)Normal operation means that performance of each component as well
as of the entire assembly of the methane-monitoring system is in conformance
with the functions for which it was designed and for which it was tested by
(l)Flame arrester means a device so constructed that it will prevent
propagation of flame or explosion from within the unit of which it is part to
a surrounding flammable mixture.
(m)Intrinsically safe equipment and circuitry means equipment and
circuitry that are incapable of releasing enough electrical or thermal energy
under normal or abnormal conditions to cause ignition of a flammable mixture
of the most easily ignitable composition.
(n)Fail safe means that the circuitry of a methane-monitoring system
shall be so designed that electrical failure of a component which is
critical in MSHA's opinion will result in deenergizing the
methane-monitoring system and the machine or equipment of which it is a
[31 FR 10607, Aug. 9, 1966, as amended at 39 FR 24003, June 28, 1974; 43 FR
12316, Mar. 24, 1978]