The optimal conditions for activating zeolites NaX and LiX have been determined through the design of experiment using the general criterion, Harrington's desirability function. The effect of four factors, i.e., temperature, heating rate, composition, and specific volume of purge gas, on the nitrogen/oxygen par tition coefficient for zeolite NaX has been studied. It has been established that the presence of carbon dioxide in purge gas during zeolite activation positively affects the partition coefficient and increases the capacity of zeolite to adsorb nitrogen.