In this work, a generalized expression for gas permeation, which takes account of thepartial pressure, has been developed for both liquid membranes and fixed carrier membranes. The gas permeation behaviors with varying partial pressure were analyzed based on the generalized expression. Based on the expression for the permeance, the facilitated transport parameters of an immobilized liquid membrane and a fixed carrier membrane, including diffusion coefficient of uncomplexed solute and solute-carrier complex as well as reaction equilibrium constant, were calculated by fitting the experimental data of the permeance varying with the partial feed pressure. The calculated parameters agreed well with those in the literature. To check the present expression and the calculated parameters, the gas permeance of two kinds of immobilized liquid membranes and a fixed carried membrane were predicted under varying partial pressure. The predicted results were in satisfactory agreement with the experimental data. Moreover, the prediction for the effects of membrane thickness, carrier concentration and equilibrium constant on the relationship between gas permeance and partial pressure has been carried out. (C) 2013 Elsevier B.V. All rights reserved.