Selected strongly adsorbed gaseous impurities are removed from a gas stream by pressure swing adsorption in an adsorption system which includes a single adsorption vessel, a gas storage vessel and a single gas pump. Feed gas is pumped at a selected adsorption pressure cocurrently through the adsorption vessel, which contains an adsorbent that selectively adsorbs the selected impurity or impurities. The less strongly adsorbed components of the gas mixture pass out the adsorption vessel through the nonadsorbed gas outlet end of the adsorption vessel. When the adsorbed gas front reaches a certain point in the adsorption vessel, the adsorption step is terminated and gas is countercurrently transferred from the adsorption vessel to a gas storage vessel, optionally with use of the gas pump. The adsorption vessel is then countercurrently evacuated by use of the pump and a selected gas-enriched product is recovered and sent to storage or further processed in downstream treatment operations. Following bed regeneration, the adsorption vessel is partially repressurized by transferring gas from the storage vessel to the adsorption vessel, optionally with use of the pump, and then the adsorption vessel is pressurized to the selected adsorption pressure using the pump.