A process is disclosed for producing hydrogen for a hydrogen consuming process comprising obtaining a gas stream containing hydrogen from a steam reforming hydrogen plant, sending the gas stream to a pressure swing adsorption unit to be separated into a hydrogen stream and a fuel gas stream; purging the pressure swing adsorption unit with an external purge gas stream from a hydroprocessing unit off gas; treating the off gas with a thermal swing adsorption unit to remove water and other impurities prior to purging the pressure swing adsorption unit; and using a protective adsorbent layer in the pressure swing adsorption unit at the product-hydrogen end of the bed to adsorb impurities from the external purge gas.