dust standard when quartz is present

dust standard when quartz is present Sec. 205. In coal mining operations where the concentration of respirable dust in the mine atmosphere of any working place contains more than 5 per centum quartz, the Secretary of Health, Education, and Welfare shall prescribe an appropriate formula for determining the applicable respirable dust standard under this title for such working place and the Secretary shall apply such formula in carrying out his duties under this title.