Correction of sampler-to-sampler comparisons based on aerosol size distribution.
This article explains a simple method for correcting a sampler-to-sampler ratio for changes in size distribution by computing a bias factor that relates the measured ratio with a ratio determined from equations that describe the collection efficiency curves of the samplers while taking size distribution into account. Laboratory trials were conducted to determine whether the resulting bias factor is independent of aerosol size distribution. During these studies, a 3-piece cassette and respirable cyclone were compared with an inhalable sampler in both a still-air chamber and a moving-air chamber operated at 0.2 m/sec and 1.0 m/sec. An ISO test dust of various size fractions was generated to produce an aerosol with mass median aerodynamic diameter ranging from 1.4 microm to 10.1 microm. An organic dust consisting of ground grain material was also applied to the still-air chamber to demonstrate differences between dust types. Results showed that the bias value was significantly different between dust types for both the cyclone/ inhalable (p=0.001) and cassette/inhalable (p=0.033) comparisons but was not different between wind conditions for either comparison. All but one comparison had insignificant slopes when comparing the bias value with median diameter, indicating that the bias value could be used to correct for size distributions in most conditions. However, bias values determined when comparing the cyclone with the inhalable sampler in the still-air condition produced a positive slope for median diameters less than 4 microm (p=0.008). Further research is needed to determine why the actual cyclone/inhalable ratio decreases relative to the expected ratio as the proportion of respirable particles increases. These results suggest that, for most conditions, the size-distribution compensation can be applied to sampler-to-sampler correlations provided that the original comparison was performed with the same dust type.
O'Shaughnessy
Patrick T
PT
The University of Iowa , Occupational and Environmental Health, Iowa City, Iowa 52242, USA. patrick-oshaughnessy@uiowa.edu
Lo
Julie
J
Golla
Vijay
V
Nakatsu
Jason
J
Tillery
Marvin I
MI
Reynolds
Stephen
S
D000336:Aerosols / Q000032:analysis* / Q000737:chemistry; D000395:Air Pollutants, Occupational / Q000032:analysis*; D004391:Dust / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods*; D004867:Equipment Design; D016273:Occupational Exposure / Q000032:analysis*; D010316:Particle Size; D015203:Reproducibility of Results
D000336:Aerosols; D000395:Air Pollutants, Occupational; D004391:Dust