This specification covers requirements for oxygen concentrators. Oxygen concentrators provide a safe source of oxygen-enriched air for patients in need. They are devices that raise the level of inspired oxygen by separating nitrogen or oxygen from ambient air. Oxygen concentrators fall into two main classes according to the means whereby gas separation is effected, namely: oxygen concentrators in which oxygen selectively permeates or transports through a membrane or lattice, and pressure swing absorbers (PSA) in which air is exposed at a certain pressure to molecular sieve material that selectively retains nitrogen and other components until they are subsequently released when the pressure is reduced. Oxygen concentrators shall comply with the following requirements: protection against hazards from unwanted or excessive radiation; protection against excessive temperatures, and other safety hazards; accuracy of operating data and protection against hazardous output; and constructional requirements.