30 CFR § 7.508
Harmful gas removal components.
(a) Each refuge alternative shall include means for removing
(1) Purging or other effective procedures shall be provided for the
airlock to dilute the carbon monoxide concentration to 25 ppm or less
and the methane concentration to 1.0 percent or less as persons enter,
within 20 minutes of persons deploying the refuge alternative.
(2) Chemical scrubbing or other effective procedures shall be
provided so that the average carbon dioxide concentration in the
occupied structure shall not exceed 1.0 percent over the rated
duration, and excursions shall not exceed 2.5 percent.
(i) Carbon dioxide removal components shall be used with breathable
air cylinders or oxygen cylinders.
(ii) Carbon dioxide removal components shall remove carbon dioxide
at a rate of 1.08 cubic feet per hour per person.
(3) Instructions shall be provided for deployment and operation of
the harmful gas removal component.
(b) The harmful gas removal component shall meet the following
requirements: Each chemical used for removal of harmful gas shall be--
(1) Contained such that when stored or used it cannot come in
contact with persons, and it cannot release airborne particles.
(2) Provided with all materials; parts, such as hangers, racks, and
clips; equipment; and instructions necessary for deployment and use.
(3) Stored in an approved container that is conspicuously marked
with the manufacturer's instructions for disposal of used chemical.
(c) Each harmful gas removal component shall be tested to determine
its ability to remove harmful gases.
(1) The component shall be tested in a refuge alternative structure
that is representative of the configuration and maximum volume for
which the component is designed.
(i) The test shall include three sampling points located vertically
along the centerlines of the length and width of the structure and
equally spaced over the horizontal centerline of the height of the
(ii) The structure shall be sealed airtight.
(iii) The operating gas sampling instruments shall be placed inside
the structure and continuously exposed to the test atmosphere.
(iv) Sampling instruments shall simultaneously measure the gas
concentrations at the three sampling points.
(2) For testing the component's ability to remove carbon monoxide,
the structure shall be filled with a test gas of either purified
synthetic air or purified nitrogen that contains 400 ppm carbon
monoxide, ±5 percent.
(i) After a stable concentration of 400 ppm, ±5 percent,
carbon monoxide has been obtained for 5 minutes at all three sampling
points, a timer shall be started and the structure shall be purged or
carbon monoxide otherwise removed.
(ii) Carbon monoxide concentration readings from each of the three
sampling instruments shall be recorded every 2 minutes.
(iii) The time shall be recorded from the start of harmful gas
removal until the readings of the three sampling instruments all indicate a carbon
monoxide concentration of 25 ppm or less.
(3) For testing the component's ability to remove carbon dioxide,
the carbon dioxide concentration shall not exceed 1.0 percent over the
rated duration and excursions shall not exceed 2.5 percent under the
(i) At 55 ºF (±4 ºF), 1 atmosphere (±1 percent), and 50 percent (±5 percent) relative
(ii) At 55 ºF (±4 ºF), 1 atmosphere (±1 percent), and 100 percent (±5 percent) relative
(iii) At 90 ºF (±4 ºF), 1 atmosphere (±1 percent), and 50 percent (±5 percent) relative
(iv) At 82 ºF (±4 ºF), 1 atmosphere (±1 percent), and 100 percent (±5 percent) relative
(4) Testing shall demonstrate the component's continued ability to
remove harmful gases effectively throughout its designated shelf-life,
specifically addressing the effects of storage and transportation.
(d) Alternate performance tests may be conducted if the tests
provide the same level of assurance of the harmful gas removal
component's capability as the tests specified in paragraph (c) of this
section. Alternate tests shall be specified in the approval