The effects of NH3-plasma and N-2-Plasma treatments on rubbery polyethylene (PE) membranes on the permeation behavior for carbon dioxide (CO2), O-2, and N-2 were investigated with permeability measurements. The NH3-plasma and N-2-plasma treatments on PE membranes increased both the permeation coefficient for CO2 and the ideal separation factor for CO2 with respect to N-2 For O-2 transport, both the permeation coefficient for O-2 and the ideal separation factor for O-2 with respect to N-2 were increased. NH3-plasma and N-2-Plasma treatments on polymer membranes possibly bring about an augmentation of permeability and permselectivity simultaneously. (c) 2006 Wiley Periodicals, Inc.