L. 91-173, as amended by Pub. Active workings means any place in a surface coal mine or the surface work area of an underground coal mine where miners are normally required to work or travel.
Concentration means a measure of the amount of a substance contained per unit volume of air.
Sampling device approvals issued by the Secretary of the Interior and Secretary of Health, Education and Welfare are continued in effect. Surface coal mine means a surface area of land and all structures, facilities, machinery, tools, equipment, excavations, and other property, real or personal, placed upon or above the surface of such land by any person, used in, or to be used in, or resulting from, the work of extracting in such area bituminous coal, lignite, or anthracite from its natural deposits in the earth by any means or method, and the work of preparing the coal so extracted, including custom coal preparation facilities. Work position means an occupation identified by an MSHA code number describing a location to which a miner is assigned in the performance of his or her normal duties. L. 91-173 as amended by Pub.