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You've just been thrown out of the airlock with out a spacesuit. However, you do happen to be wearing a SCUBA style breathing apparatus. How long would the vacuum take to kill you, even though you have access to oxygen?

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closed as off-topic by MozerShmozer, Mołot, Josh King, James, Azuaron Apr 27 '17 at 20:48

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  • $\begingroup$ There is probably some relevant info in the answers to this question: worldbuilding.stackexchange.com/questions/78873/… $\endgroup$ – adaliabooks Apr 27 '17 at 17:22
  • $\begingroup$ Pretty bad management if the organisers mistakenly put scuba gear instead of spacesuits on board the spacecraft. In the unlikely event you survive I suggest you complain to the highest authorities. $\endgroup$ – Kilisi Apr 27 '17 at 20:39
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A SCUBA style breathing apparatus wouldn't significantly extend your survival time in a vacuum. In fact it might make your already fatal situation worse.

Without access to oxygen your timeline of usable consciousness in a vacuum is 6-9 seconds with death following soon after.

Since the only thing that would be pressurized would be your respiratory system. their is a significant pressure differential between your insides and the vacuum of space that is only contained by your fleshy body. We call damage caused by such pressure differentials Barotrauma. In addition to that it's highly plausible that that same differential would be enough to blow the mouthpiece out of your mouth.

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  • $\begingroup$ I'm actually a little curious how much barotrauma one might have. With scuba the regulator should restrict the pressure based on the difference between the vacuum outside and the pressure inside your lungs. Given that the max pressure lungs can withstand is about 2.8psi, the big limit would be the partial pressure of O2 required to stay conscious. Pure oxygen in a scuba tank might actually be sufficient to keep you conscious without requiring pressures that could cause Barotrauma. $\endgroup$ – Cort Ammon Apr 27 '17 at 17:53
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    $\begingroup$ @CortAmmon See worldbuilding.stackexchange.com/a/78877/26175 for an explanation of why we can't both prevent barotrauma and provide a breathable amount of gas even using pure oxygen. $\endgroup$ – sphennings Apr 27 '17 at 17:55
  • $\begingroup$ Yes, but remember that the mask isn't a perfect seal. Your airways are attached to your ears and eyes via sinus canals, for example. $\endgroup$ – CaM Apr 27 '17 at 17:55
  • $\begingroup$ The other WB question does point out that with a sealed mask you can go beyond the Armstrong limit (For a short time). If your lips can seal the pressure of the O2, that part would be considered sealed. Your eyes and ears may create openings to vacuums above the epiglottis, but they are certainly going to be flow-rate limited, so you should be able to sustain an above-vacuum pressure. Once you have a lung full of air, mostly close the glottis, fully close the lips and regulator, now you just have to deal with the outflow of air through your eyes and (presumably) burst eardrums. $\endgroup$ – Cort Ammon Apr 27 '17 at 18:04
  • $\begingroup$ I wouldn't call it enjoyable, but it beats having the vacuum of space strip the oxygen from your hemoglobin! $\endgroup$ – Cort Ammon Apr 27 '17 at 18:06
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I suspect the SCUBA mask would be insufficient to keep you from dying from asphyxiation.

While a SCUBA mask may be waterproof, the vacuum of space is a slightly different degree of pressure differential, and one for which your mask isn't designed. I think the mask's seal would be incapable of preventing the air from escaping into space.

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  • $\begingroup$ Could the suction of you breathing in create a temporary seal to prevent air from escaping? $\endgroup$ – Hyperdrive Enthusiast Apr 27 '17 at 17:26
  • $\begingroup$ Vacuum is a pretty strong force. what-if.xkcd.com/6 $\endgroup$ – CaM Apr 27 '17 at 17:28
  • $\begingroup$ In the Martian, when Mark Watney removes air from the Hab, he mentions that breathing in can create a air tight seal. I don't know if it would work in a vacuum though. $\endgroup$ – Hyperdrive Enthusiast Apr 27 '17 at 17:34
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I believe you'd be frozen solid before you could think about breathing.

Nope! https://www.quora.com/How-long-would-it-take-for-a-human-being-to-freeze-solid-in-outer-space

looks like it would take a while, or forever, to freeze.

The pressure differential would make it impossible to breathe. Upon being released into space if you don't exhale the loss of pressure would cause your lungs to burst. Any air in that tank, supposing you can actually suck air out of it, wouldn't make it to your lungs as it'd go right out of your mouth into space.

Also I don't think you could keep oxygen in your blood at that pressure, and you'd die of hypoxia.

So long story short, you die in seconds, with or without a scuba apparatus. In fact, the only use I can think of for a scuba apparatus in space would be to chuck it in the opposite direction of your ship, to slow or reverse your velocity away from said ship (not that it would help much, but still).

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