The volumetric method has been used to study the adsorption properties of zeolites CaA, NaX, and CaNaA; adsorption isotherms and adsorption capacities for nitrogen, oxygen, and air have been obtained. The nitrogen/oxygen selectivity values of zeolites have been determined. The experimental adsorption isotherm of air has been compared with the adsorption isotherm obtained for the pure components. The experiments have revealed that the most promising zeolite for use in a membrane-adsorption oxygen concentrator is zeolite CaNaA.