30 CFR § 71.101
Respirable dust standard when quartz is present.
When the respirable dust in the mine atmosphere of the active workings
contains more than 5 percent quartz, the operator shall continuously maintain
the average concentration of respirable dust in the mine atmosphere during
each shift to which each miner is exposed at or below a concentration of
respirable dust computed by dividing the percent of quartz into the number
10. Concentrations shall be expressed in milligrams per cubic meter of air as
measured with an approved sampling device and in terms of an equivalent
concentration determined in accordance with §71.206
sampling devices; equivalent concentrations).
EXAMPLE: The respirable dust associated with a designated work position
contains quartz in the amount of 20%, Therefore, the average concentration of
respirable dust in the mine atmosphere associated with that designated work
position shall be continuously maintained at or below 0.5 milligrams of
respirable dust per cubic meter of air (10/20=0.5 mg/m(sub)3).
Subpart C--Sampling Procedures
AUTHORITY: Secs. 101 and 103(h), Federal Mine Safety and Health Act of 1977, Pub.
L. 91-173, as amended by Pub. L. 95-164, 91 Stat. 1291 and 1299 (30 U.S.C.
811 and 813(h))), unless otherwise noted.
SOURCE: 45 FR 80757, Dec. 5, 1980, unless otherwise noted.
For further information: See MSHA's Program Policy Manual