Embodiments of methods for controlling impurity buildup on adsorbent for a pressure swing adsorption (PSA) process are provided. The method comprises the steps of operating the PSA process including performing (a) a first depressurizing equalization step, and (b) a providing purge step. Impurities are sensed in an effluent from the PSA process. If the impurities sensed in the effluent have reached a predetermined upper impurity level, then the PSA process is operated including performing (b) and not (a).