Two com. membrane modules (polysulfone and polyimide ones) were used for studying permeation of pure CO2, N-2 and O-2 at 288-303 K and gas flow rate 0.075 kmol/h (transmembrane pressure drop 0.2-7 bar). Permeation coeffs. of the gases and approx. ideal sepn. Factors were detd. The results were presented as products of permeation coeffs. and membrane surface. The polysulfone membrane was more suitable for sepn. of the gas mixts. than the polyimide one.