How Airplane Oxygen Masks Work Given They Aren’t Hooked to Tanks & How Planes Get Oxygen at Altitude
24
November

By Adem Lewis / in , , , , , , , , , , , , , , , , /


Because the economics of having large oxygen
tanks aboard airliners simply doesn’t work out (not to mention that the air quality inside
the plane would rapidly become unpleasant if fresh air wasn’t constantly supplied, regardless
of the oxygen levels), commercial airplanes have a very clever system installed to solve
the problem of ultra-low pressure atmosphere at cruising altitudes. In most modern airliners (the Boeing 787 Dreamliner
not withstanding), outside air is “bled off” from the compressor stage of the turbine engines
and eventually piped into the passenger areas. However, a bit of processing is needed first
as the compressed air is extremely hot (on the order of nearly 400 degrees Fahrenheit
or 200 degrees Celsius) at this stage. Thus, before it enters the passenger compartment,
it is first allowed to expand and is run through a heat exchanger and air cycle system to cool
it off sufficiently. This system also can work as a heater, with
some of the hot air mixed in with the cooled air to regulate cabin temperature. Once cooled and filtered, the pressurized
air, which now has sufficient oxygen density to keep people happily conscious, is piped
into the cabin area, usually at levels around 12 psi (about equivalent to atmospheric pressure
at 7,000 feet). Why 12 psi instead of something like sea-level
pressures of about 14.7 psi? 12 psi is sufficient for the majority of passengers
while simultaneously reducing the structural strain on the aircraft itself over something
like sea level atmospheric pressures. As for the air already in the cabin, this
is vented out through an outflow valve (or multiple valves in larger aircraft), usually
located near the rear of the plane. (Fun Note: Before smoking was banned on commercial
aircraft, the area around this outflow valve was generally stained dark brown from tobacco
smoke.) This outflow valve opens and closes automatically
to maintain a steady pressure inside the cabin, while the entire system is ensuring that fresh
air is continually being piped into and eventually blown out of the aircraft. In fact, while many complain of airplanes
seeming “stuffy,” this system ensures that all the air in the aircraft is being completely
replaced on average every 2-3 minutes. Yes, that means that your car, house or office
is likely significantly more “stuffy” than a commercial airplane flying at 35,000 feet. (Note: the Boeing 787 Dreamliner handles cabin
pressurization a little differently, using a modernized version of the electric compressor
system seen on many older aircraft.) Unfortunately, sometimes planes lose cabin
pressure. Whatever the cause, the loss of pressure (usually
set at atmospheric pressures past 14,000 ft) will result in oxygen masks deploying. From here, useful consciousness may only last
as little as 5-15 seconds, depending on remaining cabin pressure, which is why it’s critical
to immediately put your mask on, rather than helping someone else first. You can help them much better when you’re
not unconscious or dead. So how do these airline oxygen masks actually
work? It turns out, the economics of having a centralized
oxygen tank to provide even emergency oxygen for passengers likewise simply doesn’t add
up. Similarly, having tiny individual pressurized
oxygen tanks also isn’t feasible. In fact, these masks aren’t hooked up to any
tank or air line at all. So how are you able to breathe oxygen through
them? Science!!! While designs can vary slightly, in general,
when you pull on the device to place it over your face, the tug on the mask’s lanyard releases
a spring-loaded mechanism that sets off a small explosive charge. The resulting spark triggers a mixture of
lead styphnate and tetracene to generate heat, which will eventually cause a chemical reaction
that produces oxygen for your mask. (This is why they tell you to tug on the mask
to get the oxygen flowing- you’ve got to set off the explosive charge to get the whole
thing going.) That’s right. What you breathe through the mask didn’t begin
as pure oxygen. Rather, the plane is equipped with numerous
small chemical oxygen generators (also known as “oxygen candles,” about the size of a small
package of tennis balls) which contain a mixture of mostly sodium chlorate (NaClO3), less than
5% barium peroxide (BaO2) and less than 1% potassium perchlorate (KClO4). When these chemicals are heated by the lead
styphnate and tetracene, each undergoes a reaction that ultimately results in a fair
bit of filtered, life sustaining oxygen running through the tube to you. Of course, you might also smell a faint burning
odor, but this is nothing to be alarmed about; it just assures you that the system is working. In fact, if the plane is actually on fire,
the masks usually won’t deploy, so as not to make the fire worse with the extra oxygen. This brings us to the question of why the
plastic bag on the breathing apparatus won’t necessarily inflate as you’re using the device. More than just cosmetic, the bags serve as
something of a reservoir for oxygen. If you aren’t taking a breath at all (and
have a good seal with the mask tight against your face) the bag keeps the precious, continuously
flowing oxygen from escaping into the thin air around you, enabling more of the collected
oxygen to be taken in when you do take a breath. When this is happening, or you are breathing
out with the valves on the mask releasing much of the used air, the bag may begin to
inflate as oxygen collects. When you breathe in, it will deflate. So why won’t it always inflate at least a
little to show its working? To begin with, you may not have a great seal
with the mask on your face, particularly if you have facial hair. This will allow any produced oxygen (and air
you exhale) to more readily escape. (As long as the mask is reasonably secure
on your face, this should still provide you with sufficient oxygen to get by on as long
as the plane isn’t flying above 40,000 feet and the pilot does his or her job and gets
the plane down below 10,000 feet as rapidly as safely possible. And if you’d like to see the procedures
generally used by commercial pilots for this, go check out Mentour Pilot’s recent video
Emergency Descend!!! Cockpit Video https://youtu.be/yHawjB2PzK0
) Even if you have a good seal, however, the
rate at which the oxygen is generated is often not enough to fully inflate the masks’ bag
before you take deep, potentially panicky breaths, deflating it. This is simply because the oxygen generation
isn’t on-demand (for the passengers anyway), but simply a continuous-flow production of
oxygen. Despite the potentially slow production, the
chemical oxygen generators do provide oxygen at a sufficient rate to sustain passengers,
generally designed such that peak oxygen production occurs right away (when the plane may be at
very high altitude) with the oxygen production rates tailing off over the course of approximately
12-20 minutes before the system burns itself out. This should be long enough for the pilots
to get the plane low enough so that the air pressure is high enough for (relatively) normal
atmospheric breathing. And if you’ve ever been lucky enough to be
in this sort of situation, you know that those pilots can get the plane from altitudes like
35,000+ feet to safer atmospheric levels in a surprisingly small amount of time in an
emergency. Speaking of good timing being critical to so many aspects of life, Vincero!… Bonus Facts:
• As a result of the way the system works for pressurizing the airplane cabin and keeping
a steady supply of fresh air, the humidity levels are ultra-low, making it so you dehydrate
very quickly on flights. Particularly for long flights, it’s critical
then that you drink plenty of fluids. This ultra-low humidity level, combined with
the low cabin pressure, also reduces your sense of taste and smell by as much as 30%,
which is why airline food generally tastes so bland. To try to compensate for this somewhat, many
airlines make sure their food is much more strongly flavored or spiced than you’d normally
find appetizing. Fun fact about breathing which you may or
may not have ever noticed before- the vast majority of humans breathe out of only one
nostril at a time, with it switching periodically. The first known instance of someone studying
this “nasal cycle” was German nose specialist, Richard Kayser in 1895. How your nose accomplishes this switch is
via erectile tissue in your nose, which is very similar to the erectile tissue in a penis
or clitoris. Erectile tissue will swell up in one nostril,
mostly blocking it, and at the same time erectile tissue in the other nostril will shrink, opening
it up for breathing. Even more interesting is that depending on
which nostril you are predominately breathing out of at any given moment, it seems to greatly
affect your body and brain. For instance, a study in 1988 showed that
breathing through your right nostril significantly increases blood glucose levels, while breathing
through your left nostril has the opposite effect. Another study in 1993 showed that when you
are breathing through your right nostril, you will use significantly more oxygen than
when breathing through your left. Most interestingly of all, yet another study
published in 1994, showed that when you are breathing through your left nostril, the right
hemisphere of your brain will be more active or dominant and vice-verse when you are breathing
through your right nostril. And if you’re now wondering, even though
this switching happens naturally in a cyclical fashion, you can affect it in more ways than
just plugging one nostril or the other to force breathing through the one you want. If you lay down on one side or the other,
after around 12-15 minutes, the erectile tissue in the nostril on that side will begin to
swell up and the other side will decrease its swelling so that if you are lying on your
left side, then your right nostril will open up and your left nostril will close up. It is speculated that when you sleep on your
side, this nasal cycle could contribute to people naturally switching sides throughout
the night at very regular intervals, even if they weren’t in the slightest bit uncomfortable.


100 thoughts on “How Airplane Oxygen Masks Work Given They Aren’t Hooked to Tanks & How Planes Get Oxygen at Altitude

  1. Help get our research and writer monkeys bananas and get 15% off an awesome watch for you or as a gift for someone else at Vincero Watches: Use the code "brainfood" @ https://vincerowatches.com/brainfood

    *edit: And for those wondering, here's the link to the Mentour Pilot video (great channel by the way :-)): https://www.youtube.com/watch?v=yHawjB2PzK0

  2. There was a case where the pilots accidentally flipped a wrong switch and the air pressure in the cabin started to decrease, which caused the masks to fall, but the pilots didn't realize, and they kept flying till they passed out due to lack of oxygen and the plane crashed.

  3. So what did I get out of this video?
    Viagra causes mouth breathing!
    Yup, now you are going to go to the store. See and old man breathing through his mouth and ewwww.

    You are welcome! LOL

  4. Been beat up enough about the gulf between your abilities as a TV presenter and those as a chemist?
    Maybe re-shoot this vid. It is a pretty silly mistake.

  5. Some airplanes do use individual cylinders of oxygen at each set of masks. The 787 for example doesn't use oxygen generators.

  6. Yogis in the East have been observing nostril cycles and effects for a very long time, as part of pranayama. Sorry German guy.

  7. "Little more stuffy" – Don't know about that, given how many persons there are in that small volume inside an airplane. I would like to see some proper numbers before agreeing to that.

  8. That really explains how when I'm sick I can lie on side to open up my nose to breather. I thought it was just when I had a runny nose it was draining to one side. That's interesting, thanks!

  9. 11;50 8 Nuron & 4 Benadryl & 20/10 TumGin

    11;55 50 Xaio

    12a 20 Valerian

    12(55 6 Theanine

    Simon,
    Have you ever done a video about the glass in windows of historic age houses and why it looks like it’s been very slowly flowing like a liquid over the years? I live in Charleston and tour guides love telling people that the glass looks that way because“glass is a supercooled liquid and these windows are so old gravity has pulled the glass down to the point you see the ripples in the liquid”. I’ve heard this is a load of BS.

  10. How much of what your breathing in those masks oxygen? From what I understand breathing pure oxygen is a problem, you need some carbon dioxide etc to properly breath. Too much oxygen is why hyperventilating is a problem.

  11. It depends on the aircraft. The Navy used to fly Dc-3/C-9b’s. Those aircraft had liquid oxygen tanks in the nose if we lost pressurization. Tony

  12. A couple of mistakes you let slip by: At 03:45 the diagram reads "Purcussion"."At 04:30: NaC"L", not NaC"I". Are you not checking your facts and just reading off a teleprompter? Because that's a disappointment. I held this channel as reputable as Physics Girl or Veritasium, with the flare of VSauce, but this was it. This channel has lost credibility to me. Sorry, mate. Disliking and unsubscribing until the overall quality improves.

  13. This is one actually already knew about. But it's good that you covered it for those who don't.

    EDIT: Heeeeeeeeey! 😁 You made a shoutout to one of my favourite channels, Mentor pilot! Sweet! You should add a link to the video.

  14. I have never heard all that crazy nostril shit before. Mine only close up when I'm sick, or have allergies, and that's usually both sides. Ordinarily, I am quite aware of breathing through both nostrils, because if one is plugged up, I feel as if I am suffocating.

  15. I'll start with one word – farts.

    So yep, you ain't gonna suffer from other peoples farts for too long as the air is replaced

  16. The mention of breathing made me self conscious and in no time I needed to stand up and tell my brain off for listening too closely and upsetting my natural breathing cycle.

  17. Holy crap :O That last part about the nose, i finally know why its doing that ^^ i always wondered why my nose was so weird 😛 hahah

  18. I don't know why, but the facts about the nose really fascinated me. I have noticed the lying down one, but never wonder why and how it really works.

  19. Happily conscious isn't nearly as pleasant as happily unconscious.

    Airplanes don't seem stuffy because of the interior atmospheric conditions. It's stuffy because 200 to 300 passengers are sitting in seats that are about the size of an infant stroller.

    Nice mention of Mentour Pilot but I gave up watching that guy. I can't take anymore 30 minute videos of him sitting on his couch explaining why airplane tires are round, planes have wings, water is wet…

  20. Is it true that Winston Churchill considered surrender in ww2 I find it quite preposterous that our great leader would fathom that when the Irish never considered surrender against the empire

  21. So… YouTube recently changed their ToS, which basically says "if you're not commercially viable, that's a ban" – probably aimed at vanced users.

    I wonder how long it'll be before they extend that to creators and sponsored content.

  22. From what I know some aircraft like the 747 actually have large oxygen canisters stored away in the cargo hold rather than using the overhead compartment generators which is kind of a rare type

  23. I'm always confused by sponsored videos, I mean sure they know us well enough to understand we're all ready and waiting for the counter to say Skip Ad… but it's almost insulting and alittle backwards to think we're not going to skip past it at the start and the end with ease and with no countdown, its not what i want to see but im waiting for big ads to start appearing in the background, posters etc

  24. What is the difference between an "aviator's" and "pilot's" watch? Are those watches also suitable for flight attendants?

  25. The newer modern planes actually have oxygen tanks. Usually two. One smaller one for crew and another semi larger one for passengers. Just enough to get below pressurization flight levels.

  26. I am able to cycle my nose while laying down in 60 seconds or less, can't image it taking 15 minutes, I'd never survive a cold

  27. I had to use these once flying back from Kenya many years ago.
    They smell funny. It would be good if you can choose your own smell.
    😀

  28. From what I've seen working on airplanes, oxygen candles are mostly used on regional jets. Larger planes have clusters of oxygen tanks, usually in one of the overhead compartments. Same principal with the re-breather bag. The crew oxygen tank is in the forward avionics bay below the flight deck.

  29. Gotta love it "individual oxygen canisters are not economically viable" I mean geeze…say there's a huge risk with them on board a plane or something like that, don't give me the "they want to maximize profits" angle.

  30. From age seven My nose seldom allowed me to breath through either nostril. I noted what various fools said about how people breathed. They couldn't think, shoot, run, nor work well. Without being able to breath but through my mouth I set local records in discus, shot, middle distance, was a champion in both forms of rugby, tennis, table tennis , ballroom dancing. I impressed the Harlem GlobeTrotters enough they toured my country. My education. Surpassed most with Honours in philosophy from a top five university and attracted a tip valued at around a million dollars for my cooking steaks. I never lost a swimming race even at 32yo. There are more successes than I have time to dictate. All while ensuring quick full lungs,11.5 litres, holding and exhaling fully. My broken nose made me.

  31. Bonus facts :https://en.m.wikipedia.org/wiki/Liquid_oxygen
    https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.lockheedmartin.com/content/dam/lockheed-martin/aero/documents/sustainment/csc/service-news/sn-mag-v1-v10/V5N3.pdf&ved=2ahUKEwjeiL-UiILmAhUG11kKHcKjAosQFjAKegQIAxAB&usg=AOvVaw2nlzE149ctnpr97mtQ6pkN&cshid=1574571646244

  32. Why not just let everyone go unconsciousness (ie just give O2 to pilots, assuming "pilot" is a job that still exists and completely automated drones aren't the new plane in a few years, planes are easier to automate than cars)? They'll wake up when O2 levels go back up on decent. As a bonus those horrible 12h flights in economy will seem to be over in a few minutes.

  33. Why do you play that music ever so slightly in the background? Is the idea that it helps people stay tuned? I thought I was crazy at first haha.

  34. All this time I've been thinking I had some kind of cold or my allergies were really acting up when I lay down and one nostril closed up. Who knew! Of course now I think my nose is trying to kill me LOL

  35. Your life depends on this, if it's economicly feasible, if not, your life is worthless, yeah man, wise-up ,"wise the hell up "

  36. Although, at home your eyes don’t water and the air doesn’t. smells of kerosene… Healthier, doooo tell old chap, how?

  37. If fresh air is constantly going in and out of the cabin, what is up with the many stories about airplane air being unhealthy, as discussed here? – https://www.salon.com/2019/06/23/airlines-dirty-secret-air-quality-is-terrible-inside-airplanes/

  38. Wow that last bit really surprised me. We have the same bag on a non-rebreather mask in Healthcare to collect supplied air that's not being used yet so it's not waisted.

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