30 CFR § 57.22305
Approved equipment (III mines).
Equipment used in or beyond the last open crosscut and equipment used in
areas where methane may enter the air current, such as pillar recovery
workings, longwall faces and shortwall faces, shall be approved by MSHA under
the applicable requirements of 30 CFR parts 18
36. Equipment shall not be operated in atmospheres containing 1.0 percent or