Performance degradation of electret filter media when exposed to xylene was investigated using a custom-made exposure apparatus. Three types of electret filter media were exposed to xylene in liquid and gas phases. Experimental data indicated that the penetration percentage of di-octyl-phtalate (DOP) aerosols through electret filter media was not influenced by exposure to xylene vapors for periods up to 8 h. The filtration performance for all three types of electret filter media decreased over 30% when the samples were exposed to liquid xylene. Pressure drop changes of the filter media prior and after exposure to liquid xylene were statistically negligible. Neither morphological changes nor degradation of the polymer fibers were observed after exposure of the filter media samples to liquid xylene. Thermodynamic simulations were performed to determine the molar flux of liquid and gas phases through the filter media specimens. Experimental results obtained via capillary gas chromatography were within 4% of the predicted values. The decrease in performance was attributed to changes in the density and spatial distribution of the electret charges on the surface of the polymer fibers. (C) 2005 Elsevier Ltd. All rights reserved.