Effects of Gas Density and Viscosity on Response of Aerodynamic Particle Sizer

The performance of the aerodynamic particle sizer (APS) in an atmosphere that differs from standard calibration conditions was studied. The response of the APS for monodisperse polystyrene latex and dioctylphthalate particles ranging from 2.4 to 15.1 μm in diameter was measured in air, argon, and nitrous oxide atmospheres. The measurements indicated that particles in argon and in nitrous oxide accelerate faster than those in air. In order to postulate the mechanisms and interpret the observed results, the effects of both gas viscosity and gas density on instrument performance were considered. The particle density correction factor previously given by Wang and John (1987) (Aerosol Science and Technology. 6:191–198) was extended to include gas property effects. Good agreement was obtained between the new factor and the experimental data. Existing data obtained at a low pressure in air were also compared successfully with the developed model. Expected applications of the work are the use of the APS in an arbitrary gas or at an arbitrary temperature and pressure without a new calibration.