A “Proof of Concept” demonstration of a vehicular fuel cell air management system has been performed by VAIREX Corporation of Boulder, Colorado, USA. Pressure was generated between two proprietary Variable Positive Displacement Superchargers; one acting as a compressor, and one acting as an expander. A constant pressure of 207 kPa was maintained over a 5:l speed range. As much as 25% of the compressor driving power was recovered by the expander. The development of a dedicated fuel cell compressor/expander system based on this technology is now being sponsored by the Department of Energy.