30 CFR § 75.506-1
Electric face equipment; permissible condition; maintenance requirements.
(a) Except as provided in paragraph (b) of this section, electric
face equipment which meets the requirements for permissibility set forth in
§75.506 will be considered to be in permissible
condition only if it is maintained so as to meet the requirements for
permissibility set forth in the Bureau of Mines schedule under which such
electric face equipment was initially approved, or, if the equipment has
been modified, it is maintained so as to meet the requirements of the
schedule under which such modification was approved.
(b) Electric face equipment bearing the Bureau of Mines approval
number listed in Appendix A of this subpart will be considered to be in
permissible condition only if it is maintained so as to meet the requirements
for permissibility set forth in Bureau of Mines Schedule 2D or, if such
equipment has been modified, it is maintained so as to meet the requirements
of the schedule under which the modification was approved.
(c) Notwithstanding the provisions of paragraphs (a) and (b) of this
section, where the minimum requirements for permissibility set forth in the
appropriate Bureau of Mines schedule under which such equipment or
modifications were approved have been superseded by the requirements of this
Part 75, the latter requirements shall be
applicable.