Patent ID: 8261743

Claim:
A breathing apparatus for providing a respiratory gas to a crewmember in a cabin of an aircraft, said breathing apparatus comprising: an air inlet for admission of ambient air in said breathing apparatus, an additional gas inlet for admission of additional gas in said breathing apparatus, mixing chamber for mixing the ambient air with the additional gas, an outlet nozzle for feeding said crew member with the respiratory gas comprising said ambient air and/or additional gas, a neutralizing device for neutralizing the admission of said additional gas below a predefined cabin altitude (Z 1 ), the neutralizing device comprising: an air circuit for feeding said mixing chamber with ambient air, the pressure loss of said air circuit depending upon cabin altitude, a sealing element movable between a first position wherein the pressure loss of the air circuit is minimal and a second position wherein the pressure loss of said air circuit is increased, said sealing element being in its first position when the cabin altitude is below the predefined cabin altitude, and said sealing element being in its second position when the cabin altitude is greater than the predefined cabin altitude, a first altimetric device adapted to move the sealing element into its second position when the cabin altitude is greater than the predefined altitude, and a second altimetric device provided to pilot entry of ambient air into said apparatus as a function of the cabin altitude when the sealing element is in its second position.