Patent ID: 7082946

Claim:
A method of protecting passengers of an airplane against depressurization of a passenger cabin of the airplane at high altitude, comprising, at least at cabin altitudes higher than a predetermined altitude: feeding a breathing mask for a passenger of said airplane with oxygen at a flow rate which is an increasing function of cabin altitude via a flow-rate limiting constriction and an economizer bag, and collecting an initial fraction of gases breathed out by the passenger in a flexible re-breathing bag in communication with the mask said initial fraction corresponding to the substantially CO 2 -free dead volume of the passenger's respiratory tract; and effecting breathing by the passenger of said oxygen via the economizer bag while inhibiting breathing from the re-breathing bag and, when at least a major part of said oxygen contained in the economizer bag is breathed in, effecting re-breathing by the passenger of at least a portion of said initial fraction from the re-breathing bag.