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Given a similar mix of gases to those in our Earth's atmosphere, what is the upper limit of survivable atmospheric pressure for a human?

Could a human survive higher pressures with a gas mix unlike those on Earth?

What about mixes such as Titan or Venus, assuming one didn't instantly die from any of the other ways those planets will kill you?

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    $\begingroup$ Doesn't this largely depend on how one enters the environment? Divers can go pretty deep, but not in a rush. $\endgroup$ – kim holder Sep 2 '15 at 21:49
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    $\begingroup$ Excluding anything else but the pressure, if you're ready to breathe liquids, then we could technically survive up to the pressure where our body cavities collapse. Since those are filled with poorly compressible liquids, it would take quite some pressure to do that. Not sure we actually know at what pressure that happens tho. $\endgroup$ – TildalWave Sep 2 '15 at 22:29
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    $\begingroup$ Sorry for the vagueness of the question. My significant other asked this at 1am while I was telling him about Titan, and google was only returning information on the lower limits of livability. $\endgroup$ – Sarah Bailey Sep 3 '15 at 11:50
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    $\begingroup$ @TildalWave Interesting; would it actually be possible to breathe liquids in certain circumstances? (that sounds like a silly question, but I've found greater surprises in life) $\endgroup$ – Sarah Bailey Sep 3 '15 at 11:51
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    $\begingroup$ @SarahBourt Yes. There's even been Sci-Fi movies on the subject, but it's a real deal. That first breath has to be pretty painful tho. $\endgroup$ – TildalWave Sep 3 '15 at 12:08
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Based on saturation diving operations, it looks like the limits are as follows:

  • Compressed air: Nitrogen narcosis limits you to around four times Earth's atmospheric pressure.
  • Any gas mix: Hydreliox was used for the current depth record; insomnia and fatigue issues appear to limit you to around 65 times Earth's pressure regardless of gas mix.

Neither Titan nor Venus has any oxygen in their atmosphere. If you supplemented the atmospheric gas of Venus with oxygen, you would die in short order from carbon dioxide poisoning, long before any pressure-related effects from the 92-bar atmosphere had time to set in. Titan has a low-pressure atmosphere (only 1.5 times Earth's) that is mostly nitrogen and methane; assuming that none of the other hydrocarbons are present in toxic concentrations, you could breathe it if you had supplemental oxygen.

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    $\begingroup$ Interesting answer! It may be time for an update, it's possible further testing has been done. Also "regardless of gas mix" really just refers to whatever mixes were actually tested at the time. Without understanding the mechanism, it may or may not be an absolute limit. $\endgroup$ – uhoh Feb 9 '17 at 17:15
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    $\begingroup$ Supplementing a methane containing atmosphere with oxygen could be dangerous however... $\endgroup$ – Marius Jul 6 '17 at 9:48
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    $\begingroup$ @Marius, Titan's atmosphere is only about 4.9% methane at the surface. Once you get done adding oxygen, that'll drop to around 3.5%, below the lower explosive limit of 4.4%. $\endgroup$ – Mark Jul 6 '17 at 22:29
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The maximum pressure for long term survival in an atmosphere of 79 % nitrogen and 21 % oxygen is limited by oxygen toxicity. The limit of the partial pressure of oxygen is about 0.5 bar, the maximum pressure therefore is about 2.5 bar. For only some hours the pressure may be 4 to 5 bar, but nitrogen narcosis might be a problem. For higher pressures the amount of oxygen and nitrogen in the mix must be reduced and replaced by helium. For a total pressure of 5 bar, the amount of oxygen should be not more than 4.2 % but not less 3.2 %. The partial pressure of oxygen is then again 0.21 bar like that of normal air.
For deep sea saturation diving, a pressure of about 60 bar was survived for weeks in an atmosphere of oxygen and helium.

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The limit is probably when protein folding and other chemical reactions change due to pressure.

We can up the pressure a LOT, as we are filled with non-compressible fluids, then and force our human to breath an oxygenated liquid ... but at some point the human wouldn't function on a cellular level due to pressure affecting our functions.

https://www.nature.com/articles/ncomms14561

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