Hydrogen separation by the four-bed PSA process using layered beds of activated carbon and zeolite 5A was investigated experimentally and theoretically to recover high purity H2 from steam methane reforming off-gas. The recovery increased with increasing the residence time at given product purity because of the contact time between the impurities and the adsorbents is increased. The difference of increasing the recovery became smaller with increasing the residence time and then the recovery was not increased after 43.6 seconds of the residence time. The minimum residence time exists to obtain the maximum recovery at desired product purity (99.999%+).