The present work investigates the permeation properties of Aquivion (R) perfluorosulfonic acid (PFSA) membranes, commercialized by Solvay Specialty Polymers, in view of its possible application in the field of natural gas separation or biogas sweetening. Results have been focused on the measurement of CH4, CO2, propane and butane permeabilities at different temperatures and relative humidity, focusing the attention on investigating the material performance for CO2 separation in different experimental conditions. Aquivion (R), similarly to other PFSA materials, is highly hydrophilic, and swells consistently in humid conditions increasing its gas permeability of more than one order of magnitude with respect to value prevailing in dry conditions. Present data confirm such a behavior being the permeability of all gases and vapors tested substantially increased in presence of water. Interestingly the increase in permeability results to be similar for all the gases inspected, hence such enhanced permeation capability is not associated to a selectivity loss, as usually happens in polymeric membranes. In humid condition, therefore, the ideal separation ability of Aquivion (R) is maintained, while the potential membrane productivity increases considerably. In addition to the experimental work, a simple model derived by the analysis of permeability in heterogeneous materials has been applied to the experimental data and showed to be suitable for the description of the observed behaviors for all the gases considered.