Pressure swing adsorption process for producing oxygen comprising (a) providing at least one adsorber vessel having a first layer of adsorbent adjacent the feed end of the vessel and a second layer of adsorbent adjacent the first layer, wherein the surface area to volume ratio of the first layer is in the range of about 0.75 to about 1.8 cm−1; (b) introducing a pressurized feed gas comprising at least oxygen, nitrogen, and water into the feed end, adsorbing at least a portion of the water in the adsorbent in the first layer, and adsorbing at least a portion of the nitrogen in the adsorbent in the second layer, wherein the superficial contact time of the pressurized feed gas in the first layer is between about 0.08 and about 0.50 sec; and (c) withdrawing a product gas enriched in oxygen from the product end of the adsorber vessel.