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What air pressure can the human body survive?

  1. Aug 28, 2009 #1
    How much air pressure could a human survive in?
     
  2. jcsd
  3. Aug 28, 2009 #2

    Danger

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    I believe that is dependent upon how long s/he has to acclimatize to the environment. You could slowly increase the pressure to 10,000 psi, and the guy will probably not suffer any (since the pressure within his body will rise equivalently with the outside air). Offer him 10,000 psi via a stick of dynamite, however, and his bodily response will be significantly less comfortable.
     
  4. Aug 28, 2009 #3

    russ_watters

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    And do you intend to have this person breathing air? A person can withstand perhaps 100 atmospheres of pressure if they aren't breathing air - divers do it. If they are breathing air, the limit is just a handful of atmospheres. Not sure exactly how many it takes before oxygen becomes toxic, though.
     
  5. Aug 29, 2009 #4
    I know that you cannot breath if you are under half a meter of water. I mean you cannot use a snorkel because of the pressure on your lungs.
     
  6. Aug 29, 2009 #5

    vanesch

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    As Russ pointed out, divers are exposed to significant pressures. In fact, the main problem from a certain pressure onward is the toxicity or other unwanted biochemical effects of the breathing gasses, not the "mechanical" pressure itself. For instance, normal air becomes problematic beyond the 7 or 8 bars (although you can go to 15 bars if you're of the reckless kind). But that's because of nitrogen toxicity and oxygen toxicity, not because of the "pressure". If you adapt the breathing mixture (with helium), you can go to much higher pressures. There have been experiments with breathing liquids and then you can go to very high pressures indeed.
     
  7. Aug 29, 2009 #6

    Danger

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    Man, I'd forgotten about that. I haven't heard anything about it since the early 70's. Now I remember seeing that little rat playing around in the bottom of a tank full of super-oxygenated water. Didn't they at some point have even better results using some sort of fluorocarbon liquid in lieu of water?
    And there's one technique, which as far as I know is still rated 'Top Secret' by the US government (as if I care), wherein pilots of high-performance aeroplanes saturate their bodies with xenon gas, then have the cockpit filled with the stuff. It supposedly lets one remain functional up to about 30 g's. I incorporated that into my SF novel over 25 years ago.
     
    Last edited: Aug 29, 2009
  8. Aug 29, 2009 #7
    So can people breath in liquid oxygen? I mean apart from the fact it is cold, would it be possible?
     
  9. Aug 29, 2009 #8

    Danger

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    No. First off, as you mentioned, it is cold. One's respiratory tract and lungs would freeze solid. It would have to be evaporated first. Additionally, pure oxygen is deadly poisonous.
     
  10. Aug 29, 2009 #9

    Vanadium 50

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    Russ and Vanesch are both right. There are two problems: one is that at high enough partial pressure the N2 in air becomes toxic, and the other is that under these pressures air becomes heavier and just from mechanics breathing becomes very hard work. One can address these by going to heliox: a helium-oxygen mix, and the record is somewhere around 30 atmospheres.
     
  11. Aug 29, 2009 #10

    DaveC426913

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    You have not shared this with us. Still have signed editions?
     
  12. Aug 29, 2009 #11

    GT1

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    On recreational diving oxygen is considered toxic beyond partial pressure of 1.6bar (~67m dive on air) and Nitrogen is starting to become toxic beyond partial pressure of 3.2bar (~ 30m dive on air). If one wants to go much deeper then that he have to use mixtures with lower % of Oxygen then air, lower % of Nitrogen then air and Helium. As far as I remember the world record for "dry" diving (inside a recompression chamber) is around 700meters (~70bars).
     
  13. Aug 29, 2009 #12

    mgb_phys

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    It works for rats because they can't choke (or vomit). You can't o it so easily in primates unless they are anesthetized because of the gag reflex.

    The main practical problem for larger animals is that the carrier liquid contains such low concentrations of oxygen that you have to flow a huge volume through the lungs to get enough oxygen transferred - I forget the figures but it's something like a fire hose.
     
  14. Aug 29, 2009 #13

    Danger

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    I never submitted it for publication. It started as a grade 10 English project, and got out of hand. (Sort of like Greg's computer science project. :biggrin:) Although it is completed, as in done from beginning to end, it isn't finished. It's over 500 pages, but a large part of that should be excised. I have a couple of problems in that regard. One is that I choose my words very carefully (more than I do here), so it kind of hurts to delete them. The other is that I haven't been able to write a damned thing since I went on the anti-depressants for my ADD almost 10 years ago.
    One of the major problems is that it's supposed to be SF, not Sci-Fi or Fantasy. I extrapolated modern technology to something that I foresaw for the future. By the time I finished writing it, some bastards invented my ideas so I had to keep going back and rewriting it to get ahead. To give you an indication of the time-frame, two of the main characters are a 65-year-old Korean war Sabre pilot and a 35-year-old Viet Nam F-4 pilot. Their wives are the other two main characters, who (essential to the plot) were in a USO performance near Phnom Penh.
    If I do seek out a publisher, I'm seriously thinking of just adding an introduction page stating that it was written in the 70's and should be read with that in mind. :rolleyes:
     
  15. Aug 29, 2009 #14

    Danger

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    I was unaware of that fact about rats. I'm pretty sure, though, that I also saw a man in a tank breathing super-oxygenated fluorocarbon. In the following interview, he said that he had a huge issue with getting that first lungful in, because he felt that he was drowning, but then acclimatized rapidly. Expelling the fluid at the end of the experiment was the worst part for him. This is something that I can't cite, though, because I can't remember where I saw it. It was either SciAm or some science show on TV, but it was decades ago and my memory works for a few minutes at best.
     
  16. Aug 29, 2009 #15
    Isn't that from the movie "The Abyss"?
     
  17. Aug 29, 2009 #16

    Danger

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    A: Which part of the quote?
    B: I can't say, because I never saw 'The Abyss'.
     
  18. Aug 29, 2009 #17
    I know that liquid breathing exist but the image of a rat being placed in the stuff and slowly looking like it is dying and then it starts breathing is from the movie The Abyss. First movie with CGI btw.

     
    Last edited by a moderator: Sep 25, 2014
  19. Aug 29, 2009 #18

    DaveC426913

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    Will you let anyone read it? I would like to read it.
     
  20. Sep 6, 2009 #19

    Danger

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    Let me fix it first. :wink:
     
  21. Sep 6, 2009 #20
    I read a long time ago that xenon gas was deadly poisonous, at least that is what the San Francisco Chronical science editor wrote, after he toured the Lawrence Livermore Lab nuclear reactor during an open house a while back.
    (see http://en.wikipedia.org/wiki/Nuclear_poison)
     
  22. Sep 6, 2009 #21

    Danger

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    I'll have to look into that. The guy who told me about it was a US government subcontactor who had a pretty serious inside track. I'll have to check it out. Thanks for the heads-up; if you're correct, there's another serious re-write in my future.
     
  23. Sep 6, 2009 #22

    Astronuc

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    The SFC science editor's comment is misleading.

    Xe is a noble gas and chemically inert (more so than nitrogen) under normal conditions. It has five stable (non-radioactive) isotopes: Xe-128, 129, 130, 131, 132 and two extremely long-lived radioisotopes: Xe-134 and 136 with half-lives of >5.8E+22 yrs and >2.4E+21 yrs, respectively, i.e. they are effectively stable for radiological considerations. The Xe gas that one would purchase from a chemical supply company is NON-radioactive.

    There are three radioisotopes: Xe-133, Xe-135 and Xe-138, which are common in fission of U-235 and Pu-239, as fission products or due to decay of I-133, I-135, I-138 respectively. Less common, or less important are Xe-137 and Xe-139, which are also radioactive. They and other radionuclides of the fission reations are intentionally retained in the fuel elements where they are produced.

    One can suffocate in an inert gas since it displaces oxygen, i.e. one suffocates from lack (absence) of oxygen, not the toxicity of an inert gas. One could suffocate from breathing nothing but He, Ne, Ar, or Kr, which are also inert but not radioactive. Radon is a radioactive noble gas, which comes from the decay of heavier elements.

    Xe-135 is a significant neutron poison - i.e. it has a high absorption cross-section for thermal neutrons, and as such, it is a parasitic absorber (interferes with the chain reaction) in the fission process. However, some of the enrichment of U-235 compensates for the presence of Xe-135 which is present in saturated equilibrium in a reactor.


    As for air - the body needs a certain partial pressure of oxygen to function. Mountain climbers about 8000 ft (2400 m) may need additional oxygen, especially if they are exerting themselves. Edmund Hillary and Sherpa mountaineer Tenzing Norgay became the first climbers known to have reached the summit of Mount Everest on 29 May 1953. I seem to remember he did it without oxygen, and if that is the case, it is because Hillary's body had acclimated to high altitude, i.e. the hemoglobin in the blood is well above the level of someone who lives as sea level.

    The lack of oxygen and reduced pressure at high altitude, and dehydration, can cause pulmonary and/or cerebral oedema, which can be fatal without prompt treatment.
    http://en.wikipedia.org/wiki/Cerebral_oedema
    http://en.wikipedia.org/wiki/Altitude_sickness (High altitude cerebral oedema)

    Another effect of rapid decompression is 'caisson's disease or the bends', in which nitrogen in the blood comes out of solution and forms bubbles (emboli) which can be fatal in the brain or heart. It is certainly painful in the joints, and it can paralyze limbs if blood flow is restricted and nerves and muscles are deprived of oxgyen.

    Pressurization of cockpits at high altitude, as well as breathing an inert He, Ne, Ar, Kr, Xe mixed with oxygen is used to prevent the bends.
     
    Last edited: Sep 6, 2009
  24. Sep 6, 2009 #23
    I read someplace, I think the sci.physics newsgroup, that because the temperature of the ocean is above the critical temperature for oxygen, if oxygen were pumped to below 23,100 feet in the ocean it would be denser than seawater yet still gaseous. Bubbles of oxygen could be deposited on the seafloor provided it was below that depth and the oxygen would stay there, well at least until it dissolved into the water.
     
  25. Sep 6, 2009 #24
    From Bob S
    I read a long time ago that xenon gas was deadly poisonous, at least that is what the San Francisco Chronical science editor wrote, after he toured the Lawrence Livermore Lab nuclear reactor during an open house a while back.
    (see http://en.wikipedia.org/wiki/Nuclear_poison)
    Xenon gas is a product of nuclear fission, and has an extremely high cross section for absorbing thermal neutrons, and will quench or "poison" the reactivity in a nuclear reactor. The SF Chronical science reporter misunderstood the physicist's comment about xenon poisoning the reactor.

    [Added text from}
    http://www.statemaster.com/encyclopedia/Nuclear-reactor-physics
    Short-lived poisons and controllability
    Short-lived reactor poisons in fission products strongly affect how nuclear reactors can operate. Unstable fission product nuclei transmute into many different elements (secondary fission products) as they undergo a decay chain to a stable isotope. The most important such element is Xenon, because the isotope 135Xe, a secondary fission product with a half-life of about 9 hours, is an extremely strong neutron absorber. In an operating reactor, each nucleus of 135Xe is destroyed by neutron capture almost as soon as it is created, so that there is no buildup in the core. However, when a reactor shuts down, the level of 135Xe builds up in the core for about 9 hours before beginning to decay. The result is that, about 6-8 hours after a reactor is shut down, it can become physically impossible to restart the chain reaction until the 135Xe has had a chance to decay over the next several hours.
     
    Last edited: Sep 6, 2009
  26. Sep 6, 2009 #25

    mgb_phys

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    That bit was cut in the UK - can't be cruel to animals.

    Not by a long way, TRON was earlier (82) and the first CGI character is reckoned to be the knight in Young Sherlock (85)
     
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