Wikipedia:Reference desk/Archives/Science/2020 May 13

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May 13

Oxygen masks on planes

There's understandable concern these days[1][2] about flying on planes potentially breathing corona-infected aerosols exhaled by other passengers. On the other hand, every (US) airline seat already has an oxygen mask that can drop down in front of the passenger, and they instruct you before every flight how to use the mask.

Is there some reason they can't just start deploying those masks every flight and let the passengers wear them through the whole flight? Where does the air come from for those masks anyway? Is it actually pure oxygen, carried on board in tanks, or is it normal air brought in from outside the plane, heated, and pressurized? The latter makes more sense in terms of takeoff weight, I'd think, and hopefully it could run for as long as desired at maybe some slight cost in fuel efficiency. Thanks. 2601:648:8202:96B0:3567:50D5:8BFF:4588 (talk) 07:43, 13 May 2020 (UTC)

Emergency oxygen system is the article you want to read. --Wrongfilter (talk) 07:48, 13 May 2020 (UTC)

If you're on a plane and the masks drop down, the possibility of catching someone else's infections is the least of your worries. ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:49, 13 May 2020 (UTC)

After cabin decompression, supplying air rather than oxygen would be impractical. A mask would have to handle a large ininternal positive pressure, and even if robust and fixed firmly enough to handle it, the pressure difference would make exhaling very difficult. -- Q Chris (talk) 11:07, 13 May 2020 (UTC)

Given that most Emergency Oxygen Systems uses chemical oxygen generators (aka oxygen candles), such a solution would a) create a fire hazard, b) lead to a not insignificant amount of extra maintenance as the candles would have to be replaced between each flight, c) at a significant cost to the airlines, and d) probably not deliver enough oxygen for long distance flights (an EOS is required to deliver oxygen for "minimum 10 minutes" and considering cost and weight most are likely not designed for much more than that)... At least to my mind it would be simpler, cheaper, better, and safer to simply require all passengers to use masks, as IATA is currently recommending. WegianWarrior (talk) 11:57, 13 May 2020 (UTC)

Yes, to review, the passengers' oxygen systems are just to keep the meatbags alive until the pilots can descend. The pilots have bottled oxygen, I believe, at least on large commercial aircraft, but carrying enough for every passenger for a long period of time would be impractical and a major fire hazard. If depressurization happens at high altitude, the pilots declare an emergency and immediately descend. Air traffic control's job then is to get everything else out of their way. --47.146.63.87 (talk) 19:37, 13 May 2020 (UTC)

I do believe the polite term is "self loading cargo" instead of meatbags :) WegianWarrior (talk) 19:51, 13 May 2020 (UTC)

As to "declare an emergency and immediately descend", I was reminded of this anecdote posted 30 years ago on Usenet by one of the pilots involved:

Part 1 Part 2 (ending with a repeat of Part 1). --76.71.5.208 (talk) 21:51, 13 May 2020 (UTC)

Astonishing anecdote. It is an excellent reminder of the seriousness of altitude hypoxia - especially in its ability to distort perception, and particularly how hypoxia can degrade the pilot's ability to take simple precautionary actions, ask for help, and even to understand what is occurring.

One of the most useful trainings is FAA CAMI's hypoxia altitude chamber, in which airmen may physically experience the extraordinary physiological and psychological symptoms that simulate a high-altitude depressurization or oxygen-system-failure emergency. The human brain operates differently when deprived of oxygen; and because the human requires its brain to conduct the vital task of perception, it is usually not obvious to the person experiencing hypoxia that they are rapidly entering a very serious emergency condition.

On the reference desk, I have previously linked to the famous Four of Spades video, which was also shown during our FAA altitude training classroom session. A key thing to remember is that the airman in that video is a physically-fit, highly-intelligent pilot officer of the United States Air Force; when his brain is deprived of oxygen, the results are nearly incomprehensible: "no symptoms yet."

Nimur (talk) 19:24, 14 May 2020 (UTC)

Thank you not only for bringing us an interesting story, but one from a Usenet archive, with an impressive bang path! Beorhtwulf (talk) 20:28, 19 May 2020 (UTC)

At high altitude, the regular cabin air is air brought in from outside and pressurized: bleed air. This can't be relied on in a depressurization event because there could be engine failure or structural damage to the craft, and anyway you would need a piping system installed to deliver the air to each seat, which would be complex, heavy, and itself susceptible to failures. Also, unless the oxygen masks are airtight and have a one-way exhalation valve, they still won't protect fully against virus transmission, though they may reduce risk. --47.146.63.87 (talk) 19:37, 13 May 2020 (UTC)