Comparison of number and respirable mass concentration determinations.
NIOSH 1990 Nov; :1106-1110
An evaluation was conducted to investigate the validity of the equivalent respirable mass concentrations recommended by safety organizations. A brief review was presented of the rationale published in the 1976 and subsequent Threshold Limit Value Handbooks and other sources. Empirical relationships were derived from comparative measurements obtained with a long running midget impinger and a respirable dust sampler. It was concluded that the general relationship of 6mppcf equalling 1mg/m3 used to convert particle count concentration data to respirable mass concentration data was not valid. This conclusion was based on the fact that equivalent mass concentrations established from the empirical relationships derived from comparative impinger and respirable samples did not always agree with those recommended in the Threshold Limit Value Handbook. The rationale supporting the 6mppcf equivalent to 1mg/m3 relationship was determined to be questionable and could not be confirmed using data collected during this evaluation. Since there was a significant difference in the empirical relationships derived between count and respirable mass concentration, determinations and attempts to mathematically calculate equivalent mass concentrations were not successful. The authors conclude that equivalent respirable mass concentration limits should be empirically derived using comparative measurements obtained in the aerosol of interest.
Measurement-equipment; Analytical-methods; Control-technology; Chemical-analysis; Air-quality-monitoring; Mineral-dusts; Airborne-dusts; Fibrous-bodies; Air-sampling-equipment
Proceedings of the VIIth International Pneumoconioses Conference