Design and use of a settling chamber for sampler evaluation under calm-air conditions

A compact, low cost, and easy to operate experimental system was developed for evaluating personal samplers in a calm-air environment. The system can provide uniformly distributed monodisperse microspheres up to 69.7 mum in a quiescent environment for determining sampler efficiencies using a fluorescence method. The reference concentration was measured using one vertical and two horizontal sharp-edged probes. The vertical sampling probe met the criterion for greater than 90% sampling efficiency for upward facing cylindrical probes given by Agarwal and Liu, except at the particle size of 69.7 mum. In addition, the consistent agreement among all three reference sampling probes at all particle sizes tested implied that representative measurements of aerosol concentrations in the test section were achieved. In this study, the RespiCon (Model No. 8522, TSI Inc., St. Paul, MN, USA) and IOM (Cat. No. 225-70, SKCInc., Eighty Four, PA, USA) personal aerosol samplers were evaluated in the system with air velocities in the sampling region below 1.5 cm/s. The sampling efficiency of the IOM was near 100% at all particle sizes, while the RespiCon matched the conventional respirable and thoracic convention curves but undersampled the inhalable fraction.