[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: 30CFR33.32] [Page 167] TITLE 30--MINERAL RESOURCES CHAPTER I--MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR PART 33_DUST COLLECTORS FOR USE IN CONNECTION WITH ROCK DRILLING IN COAL MINES--Table of Contents Subpart C_Test Requirements Sec. 33.32 Determination of dust concentration. (a) Concentrations of airborne dust in the test space shall be determined by sampling with a midget impinger apparatus, and a light- field microscopic technique shall be employed in determining concentrations of dust in terms of millions of particles (5 microns or less in diameter) per cubic foot of air sampled. (b) Before a drilling test is started the surfaces of the test space shall be wetted; the test space shall be cleared of air-borne dust insofar as practicable by mechanical ventilation or other means; and an atmospheric sample, designated as a control sample, shall be collected during a 5-minute period to determine residual airborne dust in the test space. (c) A sample of airborne dust, designated as a test sample, shall be collected in the breathing zone of the drill operators during the drilling of each test hole. Time consumed in changing drill steel shall not be considered as drilling time and sampling shall be discontinued during such periods. [Sched. 25B, 25 FR 6473, July 9, 1960, as amended at 26 FR 2599, Mar. 28, 1961]