30 CFR § 57.11059
Respirable atmosphere for hoist operators underground.
For the protection of operators of hoists located underground which are part
of the mine escape and evacuation plan required under standard
57.11053, the hoist operator shall be provided with a
respirable atmosphere completely independent of the mine atmosphere. This
independent ventilation system shall convert, without contamination, to an
approved and properly maintained 2-hour self-contained breathing apparatus to
provide a safe means of escape for the hoist operator after the hoisting
duties have been completed as prescribed in the mine escape and evacuation
plan for that hoist. The hoist operator's independent ventilation system
shall be provided by one of the following methods:
(a) A suitable enclosure equipped with a positive pressure
ventilation system which may be operated continuously or be capable of
immediate activation from within the enclosure during an emergency
evacuation. Air for the enclosure's ventilation system shall be provided in
one of the following ways:
(1) Air coursed from the surface through a borehole into
the hoist enclosure directly or through a metal pipeline from such borehole;
or
(2) Air coursed from the surface through metal duct work
into the hoist enclosure, although this duct work shall not be located in
timber-supported active workings; or
(3) Air supplied by air compressors located on the surface
and coursed through metal pipe into the hoist enclosure.
A back-up system shall be provided for a hoist enclosure ventilation system
provided by either of the methods set forth in paragraphs (a)(2) and (3) of
this section. This back-up system shall consist of compressed air stored in
containers connected to the enclosure. This back-up system shall provide and
maintain a respirable atmosphere in the enclosure for a period of time equal
to at least twice the time necessary to complete the evacuation of all
persons designated to use that hoist as prescribed in the mine escape and
evacuation plan required under standard 57.11053; or
(b) An approved and properly maintained self-contained breathing
apparatus system which shall consist of a mask connected to compressed air
stored in containers adjacent to the hoist controls. The self-contained
breathing system shall provide a minimum of 24 hours of respirable
atmosphere to the hoist operator. In addition, the self-contained breathing
system shall be capable of a quick connect with the approved 2-hour
self-contained breathing apparatus above.
Subpart K--Electricity