The permeability of a 0.175 mm thick Pd-Ag tubular membrane to pure H-2 and binary mixtures of H-2/CO or H-2/CO2 was studied. The tests were performed in a wide range of temperature (523-723 K) and pressure (200-800 kPa). Pure H-2-permeation through a dense metal membrane is described by the Sieverts law. However, it was already found that the H-2 permeation does not follow the Sieverts' law when other components are present in the feed and namely CO or CO2. In this work, it is proposed a new permeation model based on the Sieverts' law considering: i) the mass transfer resistance due to the surface effects and the barrier effect due to the presence of either CO or CO2. The model was successfully validated against experimental data of hydrogen permeation for binary (H-2/CO and H-2/CO2) experiments for every working temperature and pressure. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.