FACTORS AFFECTING AEROSOL SAMPLING EFFICIENCIES AND ANALYSIS OF SAMPLING ERRORS.

Accurate aerosol measurements of ambient and industrial air environments are essential for the protection of human health. Overall aerosol sampling efficiencies of a simple thin-walled inlet, sampling isoaxially from horizontal air flow have been determined by a dynamic evaluation technique for various values of particle size, wind and inlet velocities, and inlet size. Models developed from the results discriminate the dominant mechanisms which modify the sample properties during sampling, and evaluate quantitatively the possible sampling errors for relatively wide ranges of sampling conditions. For a Stokes number or inertial parameter less than 0. 03, sampling efficiencies are 100 plus or minus 20%, while for a Stokes number larger than about 0. 3, particle losses in the inlet become significant and the loss rate has been described accurately by a new non-dimensional parameter consisting of a Stokes number, a gravitational deposition parameter and a Reynolds number.