Supplemental or first aid oxygen is oxygen that may be necessary when the air in the cabin is insufficient to support vital human functions. Protective or emergency oxygen is oxygen that may be necessary to support vital human functions because the air in the cabin is contaminated or unusable. The passenger oxygen system does not provide protective oxygen. At normal cabin pressures, air supplied by the passenger masks can be as low as 3% of total air intake by the passenger. In the event of smoke in the passenger cabin, the flight crew will unlikely drop the PSU oxygen masks as the masks provide a mixture of cabin air and pure oxygen.
Precautions while using oxygen [CFR 121.574]
When oxygen is used from any source for any reason, the following precautions are to be observed:
- Oxygen must not be used near a spark, flame, or lighted tobacco.
- When the passenger oxygen system is in use, smoking is not permitted anywhere in the cabin.
- While anyone in the flight deck is using oxygen, smoking is not permitted in the flight deck.
- Petroleum-based products (used in some cosmetics and lip balms) should be removed from the passenger’s face, as when in contact with pure oxygen, it can cause the skin/lips to burn.
- Facial hair that crosses sealing surfaces of the mask can seriously degrade the performance of the mask and reduce the amount of oxygen available to the passenger.
- When portable oxygen is no longer being used, the oxygen supply valve(s) must be closed to preserve the remaining oxygen supply and to reduce the hazard of fire.
- Crewmembers may not connect or disconnect oxygen dispensing equipment, for medical use by passengers, to or from a gaseous oxygen cylinder while any passenger is aboard the airplane. However, this does not apply to the carriage of supplemental or first aid oxygen and related equipment required by FAR 121.333.
Passenger oxygen system
When the oxygen masks drop from overhead units in the cabin, Flight Attendants will direct passengers to pull a mask down, then use the mask to cover their nose and mouth and breathe normally. Oxygen does not flow through a mask until the activation pin has been pulled free of the oxygen generator.
NOTE: Under no circumstance may the PSU oxygen be used for medical purposes.
Flight deck oxygen
The Flight Crew Oxygen system is completely separate from the cabin oxygen system. An oxygen cylinder is located in the flight deck behind the SIC. This cylinder provides oxygen to X quick-donning masks, one for each pilot, and one for the observer.
Quick-don masks enable crewmembers to put them on using only one hand, in case of emergency.
The masks have three settings for oxygen flow:
- NORM position – Supplies a cabin air and oxygen mixture on demand.
- 100% position – Supplies 100% oxygen from the cylinder only on demand.
- EMER position – Supplies a continuous flow of bottled oxygen.
Using portable oxygen bottles
When a portable oxygen bottle is used by a passenger, the preferred method of securing is to attach the bottle to the passenger over the head and shoulder with the carrying strap, to the attendant accompanying the passenger over their head and shoulder with the carrying strap, or to the adjacent seat with the seatbelt. Wrap the seatbelt around the bottle several times and secure the seatbelt. The bottle should not be hung from the tray table or seatback in front. The bottle can be secured in a piece of carry-on luggage that can then be stowed under the seat in front of the passenger, as long as the tubing does not block the egress of another passenger.
- If more than one bottle is to be used, the passenger must be instructed to watch the pressure gauge. The passenger will be told to advise a Flight Attendant when the bottle reaches 500 PSI or if they experience any problems with the flow or mask. It is, however, the responsibility of the Flight Attendant to continually monitor the passenger and the bottle gauges every 10 to 20 minutes along with the regular cabin and lavatory checks that are conducted. A bottle is considered empty at 50 PSI.
- The Flight Attendant must determine that the mask has been properly attached to either the High or Low outlet as required by the passenger’s condition. If using a portable oxygen bottle for medical purposes, use the HIGH flow outlet unless otherwise instructed by Medlink or procedures for symptoms as described in the First Aid chapter.
Considerations when using portable oxygen bottles
- Portable oxygen bottles may be used for planned or emergency medical purposes. Planned use for medical purposes must be pre-arranged by the passenger with the Department Name, if accepted by the airline. Extra bottles will be boarded for medical use. The emergency portable oxygen bottle supply may not be used for planned medical purposes. Emergency portable oxygen bottles may be used when unforeseen circumstances cause the planned oxygen supply to deplete (i.e. in-flight delays).
- When not in use, portable bottles will be properly stowed. After use, the bottles will be secured in their brackets for landing.
- At the end of the flight, the Flight Crew will be advised of the number and location of bottles used. Flight Attendants will bring the used bottles to the forward galley to give to maintenance. They will determine if they need to be refilled prior to the next departure.
- Although smoking on board is prohibited, as a reminder as it is required by regulation, no passenger may smoke within 10 feet of a passenger who is in possession of a portable oxygen bottle, regardless of if the oxygen is being consumed.
- The passenger and the oxygen equipment must not restrict access to, or use of, any emergency or regular exit or the aisle.
NOTE: Handle all high-pressure gaseous containers carefully. If the bottle falls and breaks off the pressure gauge, due to the high pressure of oxygen, the bottle can effectively become a non-exploding missile within the aircraft.