I am writing a short story in which a character is ejected out of an air lock in a space ship. He quickly re-enters (disregard how he does this) and the chamber re-pressurizes, but he is exposed to space for about nine seconds, and without oxygen for about 12 seconds. Given that the plot then has him engaging in a fire fight essentially right away, I was wondering how realistic such a scenario was.

Based on an article I've found, the character (who we'll call Dave), would lose consciousness in ~15 seconds from lack of oxygen. His blood would begin to boil and tissues expand. He could be exposed to extreme temperatures, irradiated by the sun, and even riddled by dust or debris.

Question: Assuming Dave escapes anything lethal (by some miracle of plot armor, no doubt), what are the best and worst case scenarios for his immediate physical condition once the chamber re-pressurizes? I'm basically looking for a range which I can work in.

ie: In the department of space dust/rock, the best case scenario is that he escapes injury entirely. The worst case scenario, short of lethal damage, is that his spinal cord has been punctured in several places, leaving him unable to move. I'm looking for something along those lines, though obviously with a bit more explanation/evidence to back it up.

  • $\begingroup$ "Lose consciousness in ~15 seconds from lack of oxygen": No way. Or is it that you cannot hold your breath for 15 seconds? Most people can, easily. $\endgroup$
    – AlexP
    Commented Jan 15, 2018 at 8:09
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    $\begingroup$ @AlexP won't holding some air in your lungs tear them apart because of no external pressure? That's just my guess though, maybe it doesn't work that way... $\endgroup$ Commented Jan 15, 2018 at 8:42
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    $\begingroup$ @AlexP not in vacuum... and commercial pilots flying high have about that time to use oxygen masks before they lose consciousness $\endgroup$ Commented Jan 15, 2018 at 8:42
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    $\begingroup$ That article is junk. 1) The depiction in "Mission To Mars" of what happens when exposed to space is frequently used as an object of riddicule for how stupid it is. Nothing can freeze that fast, and even less so in space since there is no convection/conduction by which to lose heat. 2) Yes, rapid sunburn is a definite possibility, but this has no fixed temperature. 3) No, it is not certain he would lose consciousness in 15 seconds, it says he could go unconscious that quickly. But this depends entirely on Dave's physical state at the moment it happens. $\endgroup$
    – MichaelK
    Commented Jan 15, 2018 at 11:19
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    $\begingroup$ @AlexP When testing how long you can hold your breath, you're usually 1) calm and collected, and 2) filling your lungs with oxygen-containing air. In a state of panic, and with nearly no actual oxygen molecules in your lungs, things progress more quickly. On a side note, the sensation that stops you from holding your breath until you lose consciousness is actually not a lack of oxygen, it's abundance of carbon doixide. That's why you can breathe helium until you pass out without feeling a thing, and having fun while you do it. $\endgroup$
    – Arthur
    Commented Jan 15, 2018 at 12:43

2 Answers 2


The wikipedia article has an acceptable summary of existing research and incidents (but make sure to read the articles in references, they are more informative).

In short:

  • loss of consciousness in about 15 sesonds
  • fatal if not repressurized in 90 seconds or so
  • lungs might burst if the person is trying to hold breath

If you worry about being riddled to dust by debris (in those 90 seconds), you have much bigger problems - like your space station being riddled to dust as well.

Temperature changes, irradiation etc. are relatively unimportant, unless your station is orbiting Mercury. The character would not have time to freeze to death - vacuum is a very good insulator, and what cooling is there by evaporation won't be so quick.

  • $\begingroup$ I agree, space dust isn't going to be an issue if the space station is in fact. A projectile moving the speed of a bullet is going to seriously damage a space station or a human being alike. Also, I would add that unless the protagonist has had ample experience being exposed in space, the most human panick reaction would be to hold breath. So either lungs burst or air cannot physically be held in. $\endgroup$
    – Neil
    Commented Jan 15, 2018 at 9:15

Perhaps the best science-based answer can be found here Survival in Space Unprotected Is Possible--Briefly All quotes are from this article.

In reality, however, animal experiments and human accidents have shown that people can likely survive exposure to vacuum conditions for at least a couple of minutes. Not that you would remain conscious long enough to rescue yourself, but if your predicament was accidental, there could be time for fellow crew members to rescue and repressurize you with few ill effects.


But death is not instantaneous. For example, one 1965 study by researchers at the Brooks Air Force Base in Texas showed that dogs exposed to near vacuum—one three-hundred-eightieth of atmospheric pressure at sea level—for up to 90 seconds always survived. ... But after slight repressurization the dogs shrank back down, began to breathe, and after 10 to 15 minutes at sea level pressure, they managed to walk, though it took a few more minutes for their apparent blindness to wear off.

With the caveat

Water and dissolved gas in the blood forms bubbles in the major veins, which travel throughout the circulatory system and block blood flow. After about one minute circulation effectively stops. The lack of oxygen to the brain renders you unconscious in less than 15 seconds, eventually killing you. "When the pressure gets very low there is just not enough oxygen. That is really the first and most important concern," Buckey says.

It's not how much oxygen is in the body (thus holding your breath is irrelevant but dangerous) but how it is ported to the brain.

Chimpanzees can withstand even longer exposures. In a pair of papers from NASA in 1965 and 1967, researchers found that chimpanzees could survive up to 3.5 minutes in near-vacuum conditions with no apparent cognitive defects, as measured by complex tasks months later.


For example, in 1965 a technician inside a vacuum chamber at Johnson Space Center in Houston accidentally depressurized his space suit by disrupting a hose. After 12 to 15 seconds he lost consciousness. He regained it at 27 seconds, after his suit was repressurized to about half that of sea level. The man reported that his last memory before blacking out was of the moisture on his tongue beginning to boil as well as a loss of taste sensation that lingered for four days following the accident, but he was otherwise unharmed.

So, extrapolated, it is reasonable to assume that perhaps ten seconds of exposure, and twenty seconds of recovery could give the results you are after.


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