30 CFR § 75.1908
Nonpermissible diesel-powered equipment--categories.
(a) Heavy-duty diesel-powered equipment includes--
(1) Equipment that cuts or moves rock or coal;
(2) Equipment that performs drilling or bolting functions;
(3) Equipment that moves longwall components;
(4) Self-propelled diesel fuel transportation units and self-
propelled lube units; or
(5) Machines used to transport portable diesel fuel transportation
units or portable lube units.
(b) Light-duty diesel-powered equipment is any diesel-powered
equipment that does not meet the criteria of paragraph (a).
(c) For the purposes of this subpart, the following equipment is
(1) Any machine or device operated by a miner; or
(2) Any machine or device that is mounted in the direct line of
sight of a job site located within 500 feet of such machine or device,
which job site is occupied by a miner.
(d) Diesel-powered ambulances and fire fighting equipment are a
special category of equipment that may be used underground only in
accordance with the mine fire fighting and evacuation plan under