Abstract
In occupational and ambient environments, there is increasing need to monitor the atmospheres in real time so that emission sources are easily identified and exposure episodes can be better understood. Recently, several instruments have been developed commercially for aerodynamic particle-size measurements. The time-of-flight instrument, including an aerodynamic particle sizer (APS33B) and an Aerosizer, is one type of real-time instrument with high resolution. The APS33B can resolve particles in the size range of 0.5-30 μm aerodynamic diameter. The device is based on the principle of particle acceleration through a nozzle in a subsonic jet expansion flow. Larger particles attain lower velocities than smaller particles due to greater inertia. The resultant particle velocity is then determined by measuring the time-of-flight between two laser beams about 120 μm apart. Each particle sizer is calibrated with monodisperse polystyrene latex particles at the factory, and the response curve is used for data analysis. Extensive investigations have shown that both aerosol characteristics and instrument operating conditions can cause the instrument to deviate from the factory calibration curve. The performance of the APS33B in terms of measurement accuracy depends on how users accommodate these deviations in their applications. This article summarizes the available information on instrument performance and recommends appropriate corrections. Cheng, Y.-S.; Chen, B.T.; Yeh, H.-C.: Performance of an Aerodynamic Particle Sizer. Appl. Occup. Environ. Hyg. 8(4):307-312; 1993.