The performance of an electrochemical membrane module for removal of CO2 from a breathing gas mixture has been studied both experimentally and theoretically. The experimental results were obtained under various operating conditions whose effects, such as CO2 input rates and current densities on the extent of CO2 separation, were studied. The observed experimental data gives good agreement with theoretical models derived. Simulation studies reveal that the gas phase mass transfer resistances in both cathode, l/kcAg and anode, l/kaAg compartments are negligible. Transfer of CO2 for the electrochemical membrane module is mainly controlled by the resistances in the electrolyte solution: that is, absorption of CO2 in the cathode, diffusion and ionic migration in the electrolyte solution, and evolution of CO2 in the anode are the controlling steps for the rate of CO2 transfer.