Performance Of A Light Scattering Dust Monitor At Various Air Velocities: Results Of Sampling In The Active Versus The Passive Mode

The Respiratory Hazards Control Branch of NIOSH routinely conducts laboratory and mine-site evaluations of dust control technologies. Gravimetric and instantaneous dust sampling instruments are used in these evaluations to measure and document dust levels to determine worker exposure. The Thermo personal DataRam (pDR) is an instantaneous sampler that uses light-scattering technology to provide relative measures of airborne respirable dust. The pDR can be used in active and passive modes to measure respirable dust levels. Tests were conducted to evaluate the sampling performance of active and passive pDR operation relative to each other and. against a gravimetric sampler (the accepted standard for respirable dust measurement). The purpose of the test was to determine if the pDR can be used effectively in the passive mode in higher velocity airflows (up to 5.1 m/s (1000 fpm)). Studies of the pDRs in both modes of operation were conducted in a controlled laboratory environment and in field situations. Dust measurements using pDR units in both modes of operation were recorded in velocities ranging from 1.0 to 5.1 m/s (200 to 1000 fpm). Tests were conducted in ambient air and in air with the addition of moisture. Results show that, although the units measure different concentrations in their respective modes of operation as compared to a gravimetric sample, the relative readings can be corrected to yield accurate dust measurements