L. 91-173, as amended by Pub. Active workings means any place at a 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.
District Manager means the manager of the Coal Mine Safety and Health District in which the mine is located. MRE instrument means the gravimetric dust sampler with a four channel horizontal elutriator developed by the Mining Research Establishment of the National Coal Board, London, England. MSHA means the Mine Safety and Health Administration of the Department of Labor. Sampling device approvals issued by the Secretary of the Interior and Secretary of Health, Education, and Welfare are continued in effect. Secretary means the Secretary of Labor or a delegate.