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    TDF Member James-S's Avatar
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    Breathing helium keeps you warmer

    I may have misunderstood but the general impression that I get is that people think breathing helium, certainly on open circuit, will make you lose heat faster than if you were breathing nitrox/oxygen. I assume that this is because of the association with getting cold if you put helium in your drysuit, but when you actually think about the physics this can't be the case. I'm only talking about breathing it here, not putting it in your suit, just to be clear. Before I ramble on explaining why, is this already accepted knowledge to everyone or am I actually picking up on a general misconception?

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    Moderator GLOC's Avatar
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    I don't think people are saying breathing helium will make you colder than breathing any other compressed gas. Can you point to specific examples?

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    TDF Member James-S's Avatar
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    Quote Originally Posted by GLOC View Post
    I don't think people are saying breathing helium will make you colder than breathing any other compressed gas. Can you point to specific examples?

    Regards
    No I don't think I can, but I have definitely heard people say things that suggested it in the past, and then I've just accepted it until now I've actually thought about it. I must be in the minority then. Nothing to see here people, apart from a small personal epiphany.

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    Established TDF Member OutOfTest's Avatar
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    To my brain it would make sense for breathing helium to make you colder as it will transfer the heat out your lungs faster and then get breathed out.

    So if this isn't the case Id be interested to hear the reason? Not that I don't believe you, I'm sure you're much more knowledgable than I.


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    Moderator GLOC's Avatar
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    Whether it transfers heat faster (or slower) than air is probably true, whether you as a diver can tell the difference is a different question.

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    Gareth

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    Interesting link on the subject

    http://www.nitroxdiver.com/Library/coldreg.html

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    GUE Tech and Cave Instructor johnkendall's Avatar
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    Quote Originally Posted by James-S View Post
    I may have misunderstood but the general impression that I get is that people think breathing helium, certainly on open circuit, will make you lose heat faster than if you were breathing nitrox/oxygen. I assume that this is because of the association with getting cold if you put helium in your drysuit, but when you actually think about the physics this can't be the case. I'm only talking about breathing it here, not putting it in your suit, just to be clear. Before I ramble on explaining why, is this already accepted knowledge to everyone or am I actually picking up on a general misconception?
    Helium has a thermal conductivity about 6 times higher than air, so it can conduct heat out of the body faster. This seems to match my practical experience too.

    HTH
    John
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    Nicotine, valium, vicodin... notdeadyet's Avatar
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    The biggest loss of heat from the lungs is evaporation.

    For conduction to transfer heat then it has to go somewhere. Where will it go in your lungs?

    I would have thought denser gases would be better at transferring heat from your lungs. It's no different to a heat pump circuit. Lungs are the heat source, breathing gas is the carrier fluid. It has to store energy to get it to the cold outside like the liquid in the pipes.

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    Administrator Wilbo's Avatar
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    from Wikipedia:

    Helium is the second least reactive noble gas, after neon, and thus the second least reactive of all elements.[40] It is inert and monatomicin all standard conditions. Because of helium's relatively low molar (atomic) mass, its thermal conductivity, specific heat, and sound speed in the gas phase are all greater than any other gas except hydrogen. For similar reasons, and also due to the small size of helium atoms, helium's diffusion rate through solids is three times that of air and around 65% that of hydrogen.[8]

    From this I read Helium (within a breathing gas) as being a reason for losing heat quicker..


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    TDF Member James-S's Avatar
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    Quote Originally Posted by johnkendall View Post
    Helium has a thermal conductivity about 6 times higher than air, so it can conduct heat out of the body faster. This seems to match my practical experience too.

    HTH
    John
    How does the heat conduction out of the body happen? Helium makes you cold in your drysuit because heat is conducted from your body to the water via the gas, and helium is a better thermal conductor so that process happens faster than with air. The same process doesn't happen with breathing gas though, because when you inhale the gas, there can be no conduction from inside to outside of the body via the gas you're breathing. The only heat loss happens when you exhale and you lose the energy that it took to heat the gas you had in your lungs. Helium has a lower specific heat capacity than nitrogen (by about 1/3), so less energy will be used in heating the gas to body temperature. The heating process with happen faster with helium that with air because of the higher thermal conductivity, but as I believe exhaled air is generally at body temperature anyway, no more energy will be spent heating helium over air (in fact less as just explained), and the rate of conductivity would actually be irrelevant.

    The only thing that I can think of that would make this wrong is if exhaled breath is normally colder than body temperature. Specifically, if the difference between inhaled and exhaled gas temperature is <70% of the difference between inhaled gas and body temperature.

    Also a paper I found on Rubicon, I've only read the abstract though so I don't know if it's actually any inconsistencies: http://archive.rubicon-foundation.or...123456789/5819
    Last edited by James-S; 12-01-2015 at 01:51 PM.


 
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