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Thread: Air & Nitrox, which first?

  1. #11
    Join Date
    Jax Beach, FL
    i've dove to 136' fsw on nitrox. it's all about the mix. you can read about it here:

    when i got nitrox certified i used to only dive nitrox after that. cuz i was stupid. then, after a few hundred dives, i realized that i was wasting money at the dive shop. when we started mixing our own, i realized we were wasting O2. now i dive nitrox based on the dive...

    • if i'm diving deep, i may dive nitrox. i may not.
    • if i'm spearfishing in freshwater, like at the lake where i am < 40' for most of my dives, i dive air
    • if i'm doing 6 dives in a day, like at the flower gardens, i'll dive nitrox every tank
    • if i'm doing a two-tank lobster dive in FL, i'll dive nitrox on tank 1, air on tank 2 (save the extra $15 for beer)
    • if i'm terrbily hungover from the night before, i'll dive nitrox

    i'm not as think as you drunk i am ...

  2. #12
    Join Date
    Islamorada, FL
    The choice may be obvious if you're diving with an Op who chooses the sites as opposed to shore diving or diving off of a private boat. In Grand Cayman for example, the first dive is typically a deep wall dive and the 2nd is a shallow reef. Nitrox would be the obvious choice to maximize bottom time on the deep dive.

  3. #13
    Join Date
    Pittsburgh, PA


    Quote Originally Posted by russp View Post
    Just finished the nitrox course and of course thought of a question the next day. If for some reason you were doing multiple dives and couldn't do them all on nitrox what do you dive first, the air or the nitrox? I came up with reasons for both but didn't know if they were valid.

    Dive deep on nitrox first to lesson nitrogen loading.
    Dive nitrox on the later shallow dive to help with off gassing.

    Anyone know the real answer?

    good qus - and has been debated all round.

    practically - i dont think it matters (assuming the dives are rather un compliacted, not too deep, not stressful etc)

    theoretically - PADI etc covers that the deepest dive should be done first.

    For me , over the years i have done air dives to the same max depth back to back (likewise for nitrox dives). My own guidelines

    a) air or nitrox dive first - no difference (assuming the dives are kept to their respective NDL, SI etc)
    b) sometimes i may feel sluggish , then i will opt for air then nitrox dive- making use of the higher o2 to "push" my O2 limits and help in the off-gassing (so i do a lots of mix gas diving as well, and i apply some of the max po2 concepts to my nitrox dives)

    in the end, i dont think (may be wrong) , that there is any definitive science for this. If you stick to to the EAD, SI and max depth, and max PO2 - coupled with good diving habits (hydration, sleep etc) - you will be fine

    we are divers ! (anyway all these decompression and gas stuff are more of an art , than a defintive science) dive away !!!!

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