[Code of Federal Regulations] [Title 30, Volume 1] [Revised as of July 1, 2006] From the U.S. Government Printing Office via GPO Access [CITE: 30CFR71.702] [Page 448] TITLE 30--MINERAL RESOURCES CHAPTER I--MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR PART 71_MANDATORY HEALTH STANDARDS_SURFACE COAL MINES AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES--Table of Contents Subpart H_Airborne Contaminants Sec. 71.702 Asbestos dust standard; measurement. (a) The 8-hour average airborne concentration of asbestos dust to which miners are exposed shall not exceed two fibers per cubic centimeter of air. Exposure to a concentration greater than two fibers per cubic centimeter of air, but not to exceed 10 fibers per cubic centimeter of air, may be permitted for a total of 1 hour each 8-hour day. As used in this subpart, the term asbestos means chrysotile, amosite, crocidolite, anthophylite asbestos, tremolite asbestos, and actinolite asbestos but does not include nonfibrous or nonasbestiform minerals. (b) The determination of fiber concentration shall be made by counting all fibers longer than 5 micrometers in length and with a length-to-width ratio of at least 3 to 1 in at least 20 randomly selected fields using phase contrast microscopy at 400-450 magnification. [41 FR 10223, Mar. 10, 1976. Redesignated at 45 FR 80756, Dec. 5, 1980]