Poly sulfone (PSF) membrane filters are employed as thermoplastic material in fabricating membranes for use in water ultratiltration systems and gas separation. However, PSF membrane filters have seldom been used in aerosol filtration. Therefore, this work clarifies the effects of PSF membrane filters on aerosol penetration. Three concentrations of casting solutions (10%, 15%, and 20%) were used to form membranes with the variously sized pores and porosities. The PSL monodisperse aerosols were applied as the challenged aerosols. The aerosol penetration was measured using a condensation particle counter. The effects of various factors, including particle size (0.038-0.81 mu m), flow rate (5.2, 10.4, and 15.61/min) and relative humidity (RH 30% and RH 70%) on the aerosol collection characteristics were evaluated. The experimental results implied that 10%, 15%, and 20% PSF membrane filters have different porosities and pressure drops across them were about 4.51, 5.81, and 7.31 kPa. The data obtained herein reveal that the aerosol penetrations of the 0.3 mu m PSL aerosol through the 10%, 15%, and 20% PSF membrane filters were around 7.5%, 3.8%, and 0.9%, respectively. The size of the most penetrating aerosol through the PSF membrane was approximately 0.05 mu m. These results demonstrate that the aerosol penetration through PSF membrane filters declines as the concentration of the casting solution increases, because the pore size inside the PSF membrane filter decreases as the concentration of the casting solution rises. Moreover, aerosol penetration through the PSF membrane filters increases obviously with the flow rate when aerosol is less smaller than 0.21 mu m. When aerosol is greater than 0.3 mu m, variations of penetration through the PSF membrane filters become smaller at different flow rates. The relative humidity does not affect the aerosol penetration through the PSF membrane filters. The 20% PSF membrane filter has a quality factor larger than the 10% and 15% PSF membrane filter over the entire range of aerosol sizes studies. (c) 2005 Elsevier Ltd. All rights reserved.