A portable oxygen concentrator includes a pair of sieve beds, a compressor for delivering air to the sieve beds, a reservoir receiving oxygen-enriched gas from the sieve beds, and an air manifold attached to the first ends of the sieve beds. A set of valves operate under the control of a controller for selectively opening and closing the valves to alternately charge and purge the sieve beds to deliver oxygen-enriched gas into the reservoir. In addition, an exhaust passage communicates with the plurality of sieve beds to deliver a flow of nitrogen evacuated from the sieve beds such that the flow of the nitrogen is directed at or across the controller to cool the controller.