Pressure swing adsorption process for oxygen production from air was studied by numerical simulation to estimate product purity, recovery, and productivity. At a fixed feed rate, maximum purity exists. In case of large feed velocity and pressure ratio, purity increases, then decreases as purge-to-feed ratio increases. Feasible region could be found in a figure showing recovery versus purity with fixed pressure ratio. From this figure, maximum recovery could be obtained for a given purity. Maximum productivity for a given purity was obtained at different operating conditions. As pressure ratio increases above 5, recovery hardly changes and productivity increases considerably.