The objective of this research was to conduct characterization, evaluation, and/or calibration studies of instrumentation used for measuring the quantity of respirable dust in mining atmospheres. Initially, this work involved the upgrading and detailed evaluation of the aerosol test chamber and the development of impactors with respirable classification characteristics. These were used as standards in the chamber for measuring the quantity of respirable dust based on either the American Conference of Governmental Industrial Hygienists or British Medical Research Council respirable dust criteria. A program was then conducted to calibrate several photometers. In addition, the mass sensitivity of the gca ram-1 photometer to water droplets in the respirable size range was determined. Three additional studies were also made in this program: (1) an experimental study was performed to ascertain the effect of crosswind, cyclone orientation, and particle size on particle sampling and penetration through the 10-mm dorr-oliver cyclone. (2) A theoretical study was conducted to refine the theory used to predict the particle collection characteristics of impactors. (3) Filter samples with known quantities of diesel and coal particles were produced and delivered to the Bureau of Mines for testing a raman scattering analysis technique to discriminate diesel particles in the presence of coal dust.