The American Association for Respiratory Care has reported a need to stockpile 5,000-10,000 mass casualty ventilators with supplemental oxygen in preparation for pandemic emergencies (1). The American Medical Association specifies oxygen concentrators supply oxygen at 5 liters per minute at ≥90% purity (2). However, these design specifications may not be the most efficient use of system resources in portable oxygen concentrators using pressure swing adsorption. A testbed was developed to investigate the system performance of an oxygen concentrator while altering the system inlet and outlet pressures and flow rates. This investigation demonstrates that a more efficient portable oxygen concentrator, which provides oxygen at <90% purity, should be considered and developed for potential use with a mass casualty ventilator.