H-2 permeation through Pd-Cu alloy membranes was carried out using pure H-2, simulated syngas, and binary H-2 gas mixtures of N-2, CO, CO2, or H2O, respectively, along with and without H2S in the feed to investigate the impact of non-hydrogen gas species on H-2 permeability at temperatures between 350 degrees C and 500 degrees C under pressures from 2.03 bar to 13.79 bar. When H2S was added to the feed, the H2S concentration was varied from 5 ppmv to 39 ppmv. The testing results indicated that the H-2 permeability through the Pd-Cu alloy membranes from pure H-2 followed Sievert's law. H2S in the feed did not affect the H-2 permeability at H2S concentrations below 39 ppmv and temperatures between 400 degrees C and 500 degrees C, indicating that the Pd-Cu separator was sulfur tolerant. From the H-2 permeation experiments with H-2 gas mixtures, it appeared that no inhibition effect from N-2, CO, CO2 and H2O on H-2 permeation was observed at temperatures between 400 degrees C and 500 degrees C. However, the inhibition effect from N-2, CO and H2O on the H-2 permeation was observed at 350 degrees C. Furthermore, the Pd-Cu separator was tested for 1031 h including 618 h exposure to 5-39 ppmv H2S and showed stable H-2 permeation flux without N-2 leakage detected, suggesting that the separator had a good thermal and structural stability. (C) 2013 Published by Elsevier B.V.