30 CFR § 75.505
Mines classed gassy; use and maintenance of permissible electric face equipment.
[STATUTORY PROVISION]
Any coal mine which, prior to March 30, 1970, was classed gassy under any
provision of law and was required to use permissible electric face equipment
and to maintain such equipment in a permissible condition shall continue to
use such equipment and to maintain such equipment in such condition.