30 CFR § 7.506
Breathable air components.
(a) Breathable air shall be supplied by compressed air cylinders,
compressed breathable-oxygen cylinders, or boreholes with fans
installed on the surface or compressors installed on the surface. Only
uncontaminated breathable air shall be supplied to the refuge
(b) Mechanisms shall be provided and procedures shall be included
so that, within the refuge alternative,--
(1) The breathable air sustains each person for 96 hours,
(2) The oxygen concentration is maintained at levels between 18.5
and 23 percent, and
(3) The average carbon dioxide concentration is 1.0 percent or less
and excursions do not exceed 2.5 percent.
(c) Breathable air supplied by compressed air from cylinders, fans,
or compressors shall provide a minimum flow rate of 12.5 cubic feet per
minute of breathable air for each person.
(1) Fans or compressors shall meet the following:
(i) Be equipped with a carbon monoxide detector located at the
surface that automatically provides a visual and audible alarm if
carbon monoxide in supplied air exceeds 10 parts per million (ppm).
(ii) Provide in-line air-purifying sorbent beds and filters or
other equivalent means to assure the breathing air quality and prevent
condensation, and include maintenance instructions that provide
specifications for periodic replacement or refurbishment.
(iii) Provide positive pressure and an automatic means to assure
that the pressure is relieved at 0.18 psi, or as specified by the
manufacturer, above mine atmospheric pressure in the refuge
(iv) Include warnings to assure that only uncontaminated breathable
air is supplied to the refuge alternative.
(v) Include air lines to supply breathable air from the fan or
compressor to the refuge alternative.
(A) Air lines shall be capable of preventing or removing water
(B) Air lines shall be designed and protected to prevent damage
during normal mining operations, a flash fire of 300 [deg]F for 3
seconds, a pressure wave of 15 psi overpressure for 0.2 seconds, and
(vi) Assure that harmful or explosive gases, water, and other
materials cannot enter the breathable air.
(2) Redundant fans or compressors and power sources shall be
provided to permit prompt re-activation of equipment in the event of
(d) Compressed breathable oxygen shall--
(1) Include instructions for deployment and operation;
(2) Provide oxygen at a minimum flow rate of 1.32 cubic feet per
hour per person;
(3) Include a means to readily regulate the pressure and volume of
the compressed oxygen;
(4) Include an independent regulator as a backup in case of
(5) Be used only with regulators, piping, and other equipment that
is certified and maintained to prevent ignition or combustion.
(e) The applicant shall prepare and submit an analysis or study
demonstrating that the breathable air component will not cause an
(1) The analysis or study shall specifically address oxygen fire
hazards and fire hazards from chemicals used for removal of carbon
(2) The analysis or study shall identify the means used to prevent
any ignition source.