The A320 ATA 35 Technical Notes are brief and to-the-point information about the Airbus A320 Oxygen Systems, including its components and their functions.


The Airbus A320 aircraft has three separate oxygen systems. These are a flight-crew oxygen system, a passenger oxygen system and a portable oxygen system. Each system has its own controls and indicators.

1. Flight Crew Oxygen System

  • High-pressure safety outlet is a frangible disk type.
  • Low-pressure safety outlet is a pressure relief valve.
  • Overboard green discharge indicator is connected to the high-pressure safety outlet and to the low-pressure safety outlet.
  • Rupture of the frangible disk is set at a cylinder pressure of 2500 to 2775 psig.
  • The pressure relief valve sets the limit of the low-pressure oxygen supply to 175 psig.
  • The pressure regulator regulates the low pressure at 65 to 94 psig.
  • REGUL LO PR on ECAM/DOOR/OXY page – Pressure switch operates when the oxygen supply pressure decreases to 50 plus or minus 5 psig
  • OXY CYL – 1850 psig
    • capacity of 77 cubic feet – An amber half-frame comes into view when the oxygen pressure is less than 1500 psig.
    • capacity of 115 cubic feet – An amber half-frame comes into view when the oxygen pressure is less than 1000 psig.
  • Each crew station has a quick-donning mask with a “demand regulator” installed.
  • Oxygen is supplied from a high-pressure oxygen cylinder to the masks.
  • Stowage box – for Quick Donning Mask.
    • Reset/Test – control
    • When Mask is removed – Oxy Sys automatically ON.
  • Microphone is installed in the mask.
  • Oxygen supply solenoid valve (LP Valve) – controlled by p/b switch in cockpit.
  • Pressure indication on – ECAM door/oxy page.
  • Overboard discharge indicator – Green blowout disc
    • After blowout – Show a yellow indicator
  • Follow precautions for oxygen servicing. (we directly replace the cylinder).
  • Oxygen flow is indicated by the blinker showing yellow and an OXY ON flag, which appears on the left door when closed.
  • The mask regulator provides either normal or pure oxygen by means of a Normal/100% selector. In the Normal position, the user breathes a mixture of cabin air and oxygen. When the selector is in the 100% position, the user will breathe pure oxygen. When the emergency rotation knob is rotated, the mask regulator supplies 100% of oxygen at a permanent positive pressure, independent of the position of the normal/100% selector. To take the mask off, the harness has to be inflated. This is done by operating the red clips.
  • Proper stowing of the mask is essential – At the end of the restowing operation, do the: IN SITU TESTING.

2. Passenger Oxygen System

  • The emergency oxygen for the passengers and the cabin attendants is supplied from emergency oxygen containers.
  • The emergency oxygen containers are installed:
    • Above the passenger seats
    • In the lavatories
    • At the cabin attendant stations
    • In the galley working areas
  • Each container has a chemical oxygen generator and two or more continuous-flow oxygen masks, each with a flexible supply hose.
  • No. of masks depends on location. Most containers have 4 masks.
  • Oxygen generator is a sodium chlorate core installed in stainless steel housing.
  • Chemical oxygen generators will supply a flow of low pressure oxygen for a minimum time of 13 minutes.
  • Demonstration oxygen masks are used to show the passengers how to use the emergency oxygen.
  • Manual release tools for the mechanic use – to manually open oxy containers.

3. Portable Oxygen System

  • Flight-crew portable device is a Protective Breathing Equipment (PBE).
  • Cabin-Attendants Portable Devices
    • HP oxygen cylinder with the continuous-flow masks
    • PBE
  • The HP oxygen cylinders with the continuous-flow masks supply first-aid oxygen to the passengers. If necessary, they can also supply oxygen to the cabin attendants. It is held in place by quick release clamps.
  • The oxygen cylinder will give a 15 min supply of oxygen at 20 liter/min.
  • The primary use of the PBE is to supply oxygen to the crew if there is a fire or an emission of smoke and/or poisonous gas. It permits them to move freely to extinguish the fire.



  • Oxygen cylinders or oxygen chemical generators are classified as dangerous material.

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