§ 71.702 Asbestos standard.
Asbestos is a generic term for a number of
asbestiform hydrated silicates that, when crushed or processed,
separate into flexible fibers made up of fibrils. As used in this part--
means chrysotile, cummingtonite-grunerite asbestos
(amosite), crocidolite, anthophylite asbestos, tremolite asbestos, and
means a fiber of asbestos that meets the criteria of
means a particle longer than 5 micrometers ([mu]m) with a
length-to-diameter ratio of at least 3-to-1.
(b) Permissible Exposure Limits (PELs)-- (1) Full-shift limit. A
miner's personal exposure to asbestos shall not exceed an 8-hour time-
weighted average full-shift airborne concentration of 0.1 fiber per
cubic centimeter of air (f/cc).
(2) Excursion limit. No miner shall be exposed at any time to
airborne concentrations of asbestos in excess of 1 fiber per cubic
centimeter of air (f/cc) as averaged over a sampling period of 30
(c) Measurement of airborne asbestos fiber concentration.
asbestos fiber concentration shall be determined by phase contrast
microscopy (PCM) using the OSHA Reference Method in OSHA's asbestos
standard found in 29 CFR 1910.1001, Appendix A, or a method at least
equivalent to that method in identifying a potential asbestos exposure
exceeding the 0.1 f/cc full-shift limit or the 1 f/cc excursion limit.
When PCM results indicate a potential exposure exceeding the 0.1 f/cc
full-shift limit or the 1 f/cc excursion limit, samples shall be
further analyzed using transmission electron microscopy according to
NIOSH Method 7402 or a method at least equivalent to that method.