(a) Shaft mines shall be provided with at least one of the following means to control the spread of fire, smoke, and toxic gases underground in the event of a fire: control doors, reversal of mechanical ventilaton, or effective evacuation procedures. Under this standard, ``shaft mine'' means a mine in which any designated escapeway includes a mechanical hoisting device or a ladder ascent.
(1) Control doors. If used as an alternative, control doors shall be--
(i) Installed at or near shaft stations of intake shafts and any shaft designated as an escapeway under Sec. 57.11053 or at other locations that provide equivalent protection;
(ii) Constructed and maintained according to Table C-3;
(iii) Provided with a means of remote closure at landings of timbered intake shafts unless a person specifically designated to close each door in the event of a fire can reach the door within three minutes;
(iv) Closed or opened only according to predetermined conditions and procedures;
(v) Constructed so that once closed they will not reopen as a result of a differential in air pressure;
(vi) Constructed so that they can be opened from either side by one person, or be provided with a personnel door that can be opened from either side; and
(vii) Clear of obstructions.
(2) Mechanical ventilation reversal. If used as an alternative, reversal of mechanical ventilation shall--
(i) Provide at all times at least the same degree of protection to persons underground as would be afforded by the installation of control doors;
(ii) Be accomplished by a main fan. If the main fan is located underground--
(A) The cable or conductors supplying power to the fan shall be routed through areas free of fire hazards; or
(B) The main fan shall be equipped with a second, independent power cable or set of conductors from the surface. The power cable or conductors shall be located so that an underground fire disrupting power in one cable or set of conductors will not affect the other; or
(C) A second fan capable of accomplishing ventilation reversal shall be available for use in the event of failure of the main fan;
(iii) Provide rapid air reversal that allows persons underground time to exit in fresh air by the second escapeway or find a place of refuge; and
(iv) Be done according to predetermined conditions and procedures.
(3) Evacuation. If used as an alternative, effective evacuation shall be demonstrated by actual evacuation of all persons underground to the surface in ten minutes or less through routes that will not expose persons to heat, smoke, or toxic fumes in the event of a fire.
(b) If the destruction of any bulkhead on an inactive level would allow fire contaminants to reach an escapeway, that bulkhead shall be constructed and maintained to provide at least the same protection as required for control doors under Table C-3.
Table C-3--Control Door Construction------------------------------------------------------------------------
Location Minimum required construction------------------------------------------------------------------------At least 50 feet from: timbered Control door that meets the
areas, exposed combustible rock, requirements for a ventilation door
and any other combustible in conformance with 30 CFR 57.8531.
material \1\------------------------------------------------------------------------Within 50 feet but no closer than Control door that serves as a
20 feet of: timbered areas, barrier to the effects of fire and
exposed combustible rock, or air leakage. The control door shall
other combustible material \1\ provide protection at leastWithin 20 feet of: any timbered equivalent to a door constructed of
areas or combustible rock, no less than one-quarter inch of
provided that the timber and plate steel with channel or angle-
combustible rock within the 20 iron reinforcement to minimize
foot distance are coated with one warpage. The framework assembly of
inch of shotcrete, one-half inch the door and the surrounding
of gunite, or other material with bulkhead, if any, shall be at least
equivalent fire protection equivalent to the door in fire and
characteristics and no other air-leakage resistance, and in
combustible material \1\ is physical strength.
within that distance.------------------------------------------------------------------------Within 20 feet of: timbered areas, Control door that serves as a
exposed combustible rock, or barrier to fire, the effects of
other combustible material \1\ fire, and air-leakage. The door
shall provide protection at least
equivalent to a door constructed of
two layers of wood, each a minimum
of three-quarters of an inch in
thickness. The wood grain of one
layer shall be perpendicular to the
wood grain of the other layer. The
wood construction shall be covered
on all sides and edges with no less
than twenty-four gauge sheet steel.
The framework assembly of the door
and the surrounding bulkhead, if
any, shall be at least equivalent
to the door in fire and air-leakage
resistance, and in physical
strength. Roll-down steel doors
with a fire-resistance rating of
1\1/2\ hours or greater, but
without an insulation core, are
acceptable if an automatic
sprinkler or deluge system is
installed that provides even
coverage of the door on both sides.------------------------------------------------------------------------\1\ In this table, ``combustible material'' does not refer to installed
wiring or track support. [50 FR 4082, Jan. 29, 1985; 50 FR 20100, May 14, 1985]