Patent ID: 8225791

Claim:
A respiratory gas supply circuit for an aircraft carrying passengers and/or crewmembers in a cabin, comprising: a source of breathable gas, at least one supply line connected to said source, a first actuating device provided on said supply line to open at least partially or close the supply of breathable gas, a respiratory device adapted to be worn on one passenger or crewmember's face, said respiratory device being connected to said supply line, and further comprising an ambient air inlet, said respiratory device providing to said one passenger or crewmember a respiratory gas to be inhaled corresponding to ambient air and/or breathable gas, said ambient air inlet further comprises a second actuating device to open at least partially or close said ambient air inlet; and, both said first and second actuating devices are operated so that at least one of said first and second actuating devices is closed at each instant of time, a first pressure sensor in the cabin configured to provide a cabin pressure signal representative of the cabin pressure, and an electronic circuit (i) determining first and second time intervals based at least in part on the cabin pressure signal and (ii) operating the second actuating device so as, (A) during a first duration corresponding to the first time interval, either to open or to close the second actuating device, and (B) during a second duration corresponding to the second time interval, to close the second actuating device if it was open during the first duration or to open the second actuating device if it was closed during the first duration, the first duration and the second duration being consecutive in time.