You’re on a Pan Am space shuttle, headed for the spinning split-level O’Neil-colony space station in low Earth orbit. It’s a pleasant flight, and you’re relaxing to the strains of Johann Strauss’s Blue Danube waltz.
Suddenly, a monolith measuring exactly 1-by-4-by-9 crashes through the rear of your spacecraft, cutting the cabin in half. You’re strapped in to your seat, so the outrushing air doesn’t blow you out, and you open your mouth and let the air escape from your lungs so they don’t rupture.
But now, you’re in vacuum. You’ll asphyxiate in minutes if you don’t find something to breathe.
But lo! Dangling from the ceiling/wall/floor of the remains of your cabin is an emergency plastic hose, attached to a still-functioning oxygen tank! You strap it to your face and inhale. It’s pure oxygen gas.
Will you be able to get enough oxygen in your lungs to stay conscious, with no outside air pressing back on your lungs? And how long before other factors of being in vacuo get the better of you?
The real worry would be lung overpressure - lungs can only stand a few PSI before they are damaged, so the regulator on the oxygen mask would have to be set very carefully.
According to wiki, the minimum partial pressure of O2 required not to pass out is 0.16 bar: Partial pressure - Wikipedia
According to diving lore, the maximum internal pressure human lungs can tolerate is equivalent to about 1 metre of water, or about 0.1 bar. Sadly, one scuba board describes how a child died by breathing air from an inverted bucket at the bottom of a swimming pool (4 feet deep) and surfacing while holding their breath.
So the answer is no, you can’t breath from a mask in vacuum. The positive internal pressure of pure oxygen that your lungs can tolerate without damage is too low to keep you oxygenated.
If you want to stretch a point; high altitude dwellers might be able to get away with less than 0.16 bar of oxygen. Bodybuilders who habitually blow up hot water bottles as a stunt might be able to contain more than 0.1 bar without damage. So a bodybuilder who lives in the Andes might just manage it… for a few minutes…
Ayup. One of the tenets of SCUBA diving is that you absolutely do not ever attempt to hold your breath while you are ascending, for exactly that reason; the reduction in external pressure means that you need to let air out of your lungs to avoid building up an excessive pressure differential.
Just popping in to say that I saw the thread title and immediately thought that I certainly would not want to breathe from the air hose attached to my vacuum.
But seriously, folks, it sounds like even with pure oxygen coming outta that tank at very low pressure, you wouldn’t be able to get enough O[sub]2[/sub] into your lungs without bursting them against an external vacuum.
Sounds like our hero needs plan B: Emergency inflatable balloons that the passengers can crawl into. Hopefully, HAL won’t cut the air hoses.
You just breathe normally the whole time. Inhaling while you ascend is fine - as long as your airway is open, the pressure will equalize itself as you go. If you’re doing a rapid ascent (which you don’t normally do, for other reasons) such that the air in your lungs is expanding at a higher rate than the lung volume is increasing as you inhale, the air will just escape, even though you think you’re inhaling.
Pressure considerations can’t be set aside, as described in the link you provide:
Apollo astronauts breathed pure oxygen for the entirety of their mission, but at reduced pressure; they suffered no ill effects.
Premature babies breathing pure O2 sometimes suffer permanent blindness and other complications.
SCUBA divers breathing ordinary atmospheric air (~20% O2) can suffer oxygen toxicity if their depth exceeds 150-200 feet. Breathing pure O2? Depths of 5-20 feet can be problematic.
The important factor is the partial pressure of O2 in whatever blend of gases you’re breathing, and that’s a function of the gas blend and the overall pressure.
For a related example of the IP’s question re dangers of pressure blowing your face off, a 2008 Darwin award nominee put a 6-bar high-power air hose up his ass, “hoping to have some fun farts.”
In the book “suiting up for space” it tells how high flyers used to do
pressure breathing, in that you let the air from the tank fill your lungs and then force
it out.
This requires some atmosphere in the cabin ,but, not a true vacuum.
