A Comparison of the Performance of Impactors and Gravimetric Samplers in Mine Airflow Conditions

"While the National Academy of Sciences has stated that gravimetric sampling technology for compliance purposes is adequate, research into various aspects of respirable dust control require data on many other parameters of airborne dust. These, in turn, have created the need to use many instruments, other than personal gravimetric samplers, in mi ne environments for dust measurement. There is a need to evaluate the performance of these instruments under conditions of potential use.As part of research in the Generic Technology Center for Respirable Dust, cascade impactors, gravimetric personal samplers and gravimetric samplers collecting dust using isokinetic sampling principles were employed for dust measurements under identical conditions in a mine airway. During the course of the experiments, 8-stage cascade impactors and gravimetric samplers drawing air isokinetically were located in the center of a mine airway at various stations. Two types of data were examined - concentration of dust and size distribution of the dust collected in the samplers. The data show that the amount of dust collected by an impactor is less than half the amount collected isokinetically. The size distributions of the dusts collected from the two instruments, though comparable, show a consistent difference in median diameters. The cause for this bias is examined.The paper presents and discusses the results of the tests, including the concentrations and size distributions obtained from the two instruments for different experimental conditions. There is a need to document the performance of various dust measuring devices in mine airflow conditions.INTRODUCTIONThe sampling of airborne dust in mines can be done for several purposes. Traditionally, dust sampling has been restricted to the gravimetric measurement of airborne respirable dust to comply with the regulations governing the mining industry. Instruments such as the MRE gravimetric sampler, and personal gravimetric samplers that have collection characteristics similar to the human respiratory system have been in use for the last two decades. Presently available instrumentation for the purpose of regulation have been considered adequate by the Committee on the Measurement and Control of Respirable Dust in Mines (National Academy of Sciences, 1980),"