Particle size distributions in underground coal mines.

This paper reports the results of a sampling program undertaken by NIOSH to determine the particle size distributions in underground coal mines. The program made use of newly developed cascade impactors capable of being operated with personal sampling pumps. Particle size distribution samples were collected at selected areas in 10 continuous mining sections in three states. Results plotted as mass frequency distributions indicate that a bimodal distribution may exist in areas away from the operations of the continuous miner. A primary size mode of about 17 micron and a secondary size mode of about 5 micron were measured consistently throughout the 10 mines studied.