Abstract: A demand flow oxygen valve for use with low pressure oxygen sources (about 5 to 75 psi). The inlet of the valve is provided with a diameter index safety system (DISS) oxygen-specific connector. The DISS connector is capable of connecting the inlet of the valve to any oxygen source having a male DISS connector at its outlet. Alternatively, a quick-disconnect connector could be provided to the valve. A single valve may be interchanged among multiple oxygen sources. A method of retrofitting existing oxygen supplies includes steps of providing the demand flow valve having a connector and connecting the valve to the existing oxygen source via the connector. An additional step includes providing a connector adapter if the existing oxygen source does not have a corresponding connector at its outlet.