This standard covers oxygen masks and breathing valves used with both panel mounted and mask mounted demand and pressure-demand oxygen regulators. Mask mounted oxygen regulators are covered under other standards, but when the mask mounted regulator incorporates an integral exhalation valve, the performance of this valve shall meet the requirements of this standard.This standard establishes the minimum performance standards for the manufacturer of demand type crewmember oxygen masks to be used with straight demand, diluter-demand and pressure-demand oxygen systems.