The gas separation properties of ethylene vinyl acetate (EVA) membranes containing 18 and 28 wt% of vinyl acetate (VA) were investigated in this study. The effects of membrane preparation conditions, such as thermal and thermal/wet phase inversion, and the type of solvent on the gas separation properties of EVA membranes were investigated. The permeation of pure O-2, N-2, CH4, and CO2 gases at different feed pressures ranging from 2 to 11 bar were examined. The results indicated that the CO2 permeability was evidently higher than those of the other gases. Furthermore, the solubility mechanism was found to be the dominant mechanism for permeation of gases through EVA membranes. Moreover, the membranes prepared using tetrahydrofuran (THF) as solvent showed higher gas permeabilities than those prepared using chloroform (CHCl3) as solvent. The results indicated that the gas permeabilities through membranes prepared using wet phase inversion technique were higher. Also, the membranes prepared by thermal/wet phase inversion method at higher temperatures showed improved gas separation properties. In addition, the membrane with higher VA content prepared using THF as solvent presents higher gas separation properties. Trade-off evaluation also showed that certain types of the prepared EVA membranes in this study have potential for commercialization. (c) 2008 Elsevier B.V. All rights reserved.