pilot wearing a mask designed for both diluted- and pressure-demand breathing
History An early 1919 high-altitude oxygen system used a vacuum flask of liquid oxygen to supply two people for one hour at . The liquid passed through several warming stages before use, as expansion when it evaporated, and absorbed
latent heat of vaporization, would make the gasified oxygen so cold that it could cause instant
frostbite of the lungs. The first successful creation for the oxygen mask was by Armenian born
Dr. Arthur Bulbulian, in the field of facial prosthetics, in 1941. Many designs of aviator's oxygen masks contain a microphone to transmit speech to other crew members and to the aircraft's radio. Military aviators' oxygen masks have face pieces that partially cover the sides of the face and protect the face against flash burns, flying particles, and effects of a high speed air stream hitting the face during emergency evacuation from the aircraft by
ejection seat or
parachute. They are often part of a
pressure suit or intended for use with a
flight helmet.
Regulations Three main kinds of oxygen masks are used by
pilots and crews who fly at high altitudes: continuous flow, dilute demand, and pressure demand. In a
continuous-flow system, oxygen is provided to the user continuously. It does not matter if the user is exhaling or inhaling as oxygen is flowing from the time the system is activated. Below the oxygen mask is a rebreather bag that collects oxygen during exhalation and as a result allows a higher flow rate during the inhalation cycle.
Diluter-demand and
pressure-demand masks supply oxygen only when the user inhales. They each require a good seal between the mask and the user's face. In a
diluter-demand system, as the altitude increases (ambient pressure, and therefore the partial pressure of ambient oxygen, decreases), the oxygen flow increases such that the partial pressure of oxygen is roughly constant. Diluter-demand oxygen systems can be used up to . ==Aviation passenger masks and emergency oxygen systems==