A system for separating oxygen from air operates at a pressure less than atmospheric. The oxygen separation system includes an entry port for ambient air, and at least two separate exhaust ports through which separate exhaust streams are drawn by separate suction sources. The oxygen separation system further includes a low-energy ionization portion that favors creation of molecular oxygen ions, and a higher-energy portion disposed between the ionization portion and one of the exhaust ports. A plurality of gas-permeable electrodes are charged to different voltages to provide the different portions inside the separator. An exhaust stream taken from the anode side of the separator is enriched in oxygen relative to ambient air.