30 CFR § 57.22232
Actions at 0.5 percent methane (I-B, II-A, II-B, IV, V-B, and VI mines).
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 24941, July 1, 1987; 52 FR 27903, July 24, 1987]