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Thread: physical risks of hydrogen?

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    New Member hirudin will become famous soon enough hirudin will become famous soon enough hirudin will become famous soon enough hirudin's Avatar
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    physical risks of hydrogen?

    Hi All!

    Newbie alert with hypothetical discussion:

    I've been reading (oh no!) the threads as well as other info on mixed gas diving... certainly the thread on diving neon was fascinating and there were some great input.

    But I was thinking about the use of hydrogen... certainly not a noble gas, it's on the same side of the periodic table as the most active elements on earth and even if you cancel out the explosive factor, you obviously have some very active compounds formed with its use; from your doghnut with your partially hydrogenated trans-fats through to HF which will kill you with a 2% body burn.

    I read the Comex articles discussing the use of hydreliox and the physical effects the divers experienced on the dives, but it certainly doesn't seem like a good idea... and I don't like the idea of partially-hydrogenating my own body fat.

    Guess I'm just interested in a discussion on the use of hydrogen and it's longer term effects.... just for yuks.

    -Jesse-

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    Re: physical risks of hydrogen?

    At mixtures containing over 4% O2 hydrogen can rapidly combine with that oxygen to form water.

    (This is commonly called "an explosion" and is really bad if it happens in your breathing loop!)

    If you're diving at a depth where a hypoxic mix of < 4% O2 is called for, AND you can keep the loop at that level RELIABLY, then it might be an option. However, you have to make sure there are no "slugs" of O2 around, etc - the technical hurdles associated with not going "boom" are pretty significant, and for shallower depths where the FO2 has to be over 4% are probably insurmountable.

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    New Member kala is an unknown quantity at this point kala's Avatar
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    Re: physical risks of hydrogen?

    Quote Originally Posted by Genesis
    At mixtures containing over 4% O2 hydrogen can rapidly combine with that oxygen to form water.

    (This is commonly called "an explosion" and is really bad if it happens in your breathing loop!)

    If you're diving at a depth where a hypoxic mix of < 4% O2 is called for, AND you can keep the loop at that level RELIABLY, then it might be an option. However, you have to make sure there are no "slugs" of O2 around, etc - the technical hurdles associated with not going "boom" are pretty significant, and for shallower depths where the FO2 has to be over 4% are probably insurmountable.
    For me CCR diving with hydrogen sounds technically too complicated. But in SCR mode it could be possible, when there is no need to add pure oxygen into loop.

    -kala-

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    Re: physical risks of hydrogen?

    In comparison to He, H is half as dense, is easily manufactured in limitless quantities and is a whole lot cheaper.

    So why doesn't anyone use it for diving?
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    RBW Member leadking is on a distinguished road leadking is on a distinguished road leadking's Avatar
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    Re: physical risks of hydrogen?

    Comex in Marseilles used hydrogen in some of the deepest open water dives on record. I toured their facility last year-very impressive.

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    Re: physical risks of hydrogen?

    Quote Originally Posted by leadking
    Comex in Marseilles used hydrogen in some of the deepest open water dives on record. I toured their facility last year-very impressive.
    Yeah sorry my reply should have read "why doesn't everyone use it".

    Those guys are using tiny fractions of O2 in their mixes though, less than the threshold for explosion.

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    Re: physical risks of hydrogen?

    Do Comex treat it as helium deco-wise? Are there benefits?

    If you used hydrogen very deep, would you flush with trimix as you came up and would that give you a deco benefit or would you just get really nasty ICD?

    Answers on a postcard...

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    Re: physical risks of hydrogen?

    It turns out that becuase of all sorts of interesting P Chem concepts O2 and Hydrogen only explode in certain preasure ranges. In other higer or lower preasures only a normal combustion is produced. Both of course require an ignition source. In a mixed gas diving book that is beyond arm reach right now it describes the safe depths that Hydrox can be breathed. Those depths are below 4 atm preasure if my memory is correct.

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    Re: physical risks of hydrogen?


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    Re: physical risks of hydrogen?

    There's some interesting reading on "Hydrogen as a breathing gas" by RW Braur at
    Rubicon Research Repository: Item 123456789/4862
    The safe FO2 limit seems to be around 4.5%. Even if you took your PO2 to 0.7, that would require you to be deeper than 146m, and you'd want a large margin for error.
    Hydrogen is narcotic, though not as narcotic as nitrogen.
    Hydrogen makes metal brittle, though the effects are part offset by oxygen.
    The benefits of Hydrogen (related to it being lighter) don't seem to really manifest until around 300-400m. The world record for SCUBA is, what, 320m? The present record for a rebreather dive is significantly shallower. I would be seriously concerned about the scrubber at those depths.

    The move to hydrogen seems to have been brought on largely because of the $ cost of Helium, but rebreathers don't waste much diluent and the $ is tanking. It was also caused because the US once had a near-monopoly on Helium, but that is no longer the case, as deposits are being exploited in the FSU.

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