CFR 30-70.101-2014 Mineral Resources. Part70:Mandatory health standards—underground coal mines. Section70.101: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 in the active workings is exposed at or below a concentration of respirable dust, 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 § 70.206 (Approved sampling devices; equivalent concentrations), computed by dividing the percent of quartz into the number 10.
CFR 30-70.101-2014 history
2014CFR 30-70.101-2014 Mineral Resources. Part70:Mandatory health standards—underground coal mines. Section70.101:Respirable dust standard when quartz is present.