Mathematical models were developed for the purge gas permeator assuming that deformation and axial diffusion were taking place during permeation. Then a comparative study for the plug flow model, deformation model, and diffusion-deformation model was done in order to establish the significance of incorporating axial diffusion and fiber deformation in the mathematical model of the purge gas permeator. The study showed that all three models were predicting nearly the same performance; hence, the simpler plug flow model is good enough and reasonably accurate for investigation of purge gas permeator.