The objective of the present study was to characterize the performance of a federal reference method (FRM) PM 10 sizeselective inlet using analysis methods designed to minimize uncertainty in measured sampling efficiencies for large particles such as those most often emitted from agricultural operations. The performance of an FRM PM 10 inlet was characterized in a wind tunnel at a wind speed of 8 km/h. Data were also collected for 20 and 25 mm particles at wind speeds of 2 and 24 km/h. Results

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... f the present sampler evaluation compared well with those of previous studies for a similar inlet near the cutpoint, and the sampler passed the criteria required for certification as a FRM sampler when tested at 8 km/h. Sampling effectiveness values for particles with nominal diameters of 20 and 25 mm exceeded 3% for 8 and 24 km/h wind speeds in the present study and were statistically higher than both the "ideal" PM 10 sampler (as defined in 40 CFR 53) and the ISO (1995) standard definition of thoracic particles (p < 0.05) for 25 mm particles leading to the potential for significant sampling bias relative to the "ideal" PM 10 sampler when measuring large aerosols.