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Thread: Air time in Tanks

  1. #1
    TadPole
    Join Date
    08/10/2008
    Location
    Bradenton FL.
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    47

    Air time in Tanks

    What is the time span that air can stay in a tank and still be good? I'm sure there are a lot of variables so I'll set some. A semi new tank, certified by LDS, filled with air to 3000 psi. Does it go "stale"? Can old air harm you? What constitutes old air?

    When you store a tank for any length of time how much pressure should you keep the tank at? And why?
    ~Craig~
    Dive to Live; Live to Dive

  2. #2
    Keep some pressure in to keep moisture out. If your tank sits around for months unused, you'd probably be better off not having your own tanks. Now I tell you

  3. #3
    Grouper Founding Member
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    07/09/2007
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    Gainesville, Fl
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    Generally speaking, air should not go "stale" and should be fine to use even after several years of sitting. I have personally used air from a tank which I believe to have been sitting for 5-10 years.

    The only time it is an issue is if there is water or oil or some other pollutant in the tank when it is filled. If the tank is clean inside, then nothing should be able to get in or out while the valve is closed and the tank is sitting pressurized, so nothing should happen to your air.

  4. #4
    Grouper
    Join Date
    08/31/2007
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    I have heard of one person who said he could tast the "stailness" in an old tank. I done know how old it was. I would guess that air would be good for at least a year. I'm figuring that because I do know that Medical o2 is good for only a year. Now were that magic number comes from, I don't know.

    But honestly, You should be using your tanks much more than that!

  5. #5
    Air can become stale or worse over very long periods.

    I heard that a guy died from breathing an old tank- turns out his tank was rusting on the inside and that had used up all his oxygen. Even Aluminum oxidizes, but it usually forms a 'protective layer' so I *think* long term storage would be more of an issue with steel tanks.

  6. #6
    Grand Master Spammer Founding Member
    Join Date
    07/11/2007
    Location
    Studio City, CA, USA
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    There is a real risk with steel tanks... if there is any moisture inside (bad), the rusting process will use up the oxygen in the air and it could very well end up with less oxygen than you need to sustain life. (If you have a nitrox analyzer, a quick check will confirm you have the same percentage you expect)

    Realistically, here's your answer: I definitely wouldn't worry about it for 6 months. 6 months to a year, and it's a judgment call. More than that, and it's definitely worth the small amount to dump the air and get the tanks re-filled. At any rate, after a long storage you'll likely need a vis inspection on your tank before it can be refilled anyway. In this case, that's probably a good thing.

    For long term storage, I'd keep 200-300psi max in the tank (but no less than 50psi, to be safe), to keep moisture out, but also to help prevent catastrophic failure in the event of a fire.

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