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In dive, manage having EAN programed into computer while diving air?

Discussion in 'Advanced Scuba' started by saridnour, Apr 13, 2020.

  1. flymolo

    flymolo DIR Practitioner

    I don't mean to beat a dead horse here, but i thought your original question was roughly, "how do I devise a reasonably safe ascent plan on a dive where halfway through I realized the wrong gas was programmed into my computer". I think having the practical skill to come up with a "close enough" approximation for that, using tables, is ultimately more useful in the long run, than the new dive computer functionality you are suggesting.
  2. EFX

    EFX Solo Diver

    # of Dives: 200 - 499
    Location: North Central Florida
    [---- table jockeys should leave the room] :(
    The dive data is there in the dive log. There may not be enough data points to give a finely tuned profile but I think it is feasible regardless of the legal (are there any?) aspects of doing this. You could simply select the new (proper) gas and tell the DC to recalculate. Once the calculation finishes the DC continues to calculate using the correct gas. Going from say, air to nitrox or mix is not a problem as you would end up with more NDL time or less deco time. The problem will be going from nitrox/mix to air where if you're late in the dive you find out you missed a deco stop or that deco is required and you've run down your gas. But still, it's better than nothing.
    [---- table jockeys may come back to the room now] :)
    Esprise Me likes this.
  3. johndiver999

    johndiver999 Solo Diver

    # of Dives: 500 - 999
    Location: Gainesville FL
    the benefits of retroactively changing your mix while underwater and during a dive would have to be balanced by the increased complexity and the significant possibility that a diver might make another mistake and (while diving air) change his mix to nitrox on accident. It is not like it is a common situation and nobody has the user's manual underwater, so why the heck would a manufacturer want to deliberately allow all this hocus-pocus?

    The dangers of punching in nitrox (when diving air) are minimized by the fact that the diver should probably just use all his air on a safety stop - assuming he is not confident that is not necessary. So the reasonable solution to this mistake ain't that complicated.

    Allowing people to deliberately go the other way (change air to nitrox underwater) and then have the computer give them directions to skip a deco stop (when they have the gas for it) seems really risky from a liability standpoint for a recreational computer manufacturer.
  4. dmaziuk

    dmaziuk Regular of the Pub

    The rate is log2 and integrating logarithmic functions is unpleasant enough already, but the load is proportional to time. You can go by average depth alone, but you could just as easily and likely just as accurately go by the phase of the moon.
  5. Blackfrogfeet

    Blackfrogfeet Registered

    # of Dives: 500 - 999
    Location: Canada
    If you look at GUE Fundamentals materials from 5+ years ago it actually includes the 30m/:20min set point for air diving with average depth/ on the fly planning for when 32% is not an available gas. Pretty sure it uses 40min at 18m though instead of 50, just because it's easier to work with uniform 5min increments between depths.

    BLACKCRUSADER Contributor

    # of Dives: I'm a Fish!
    Location: Taiwan

    Diver was on 21% air but did not change his computer from 30% nitrox. So he would be changing from 30% to 21% not the other way round. Also the diver could see his dive buddies dive computer and see it's reading as they would have been together at depth and time for the dive. I had a diver do this when he did the same as I was on 21% air and was not too close to NDL.
    He did an extended safety stop and didn't dive again till the next day.
    Esprise Me likes this.
  7. HKGuns

    HKGuns Contributor

    # of Dives: 25 - 49
    Location: Merica
    Clearly you didn't read the entire thread or you'd realize your comment is totally out of context with the subject.
  8. Wibble

    Wibble Contributor

    # of Dives: 500 - 999
    Location: UK
    I know. My point is that you *must* analyse your gas and mark up the cylinders.

    Lovely to have tech to tell you this, but why not just do best/safe/mandated practices?
  9. Wibble

    Wibble Contributor

    # of Dives: 500 - 999
    Location: UK
    Also, never miss the opportunity to kick Suunto, they won't allow you to change the gas whilst diving (e.g. if you've got it programmed for 32%, you can't change it to 21%) unless you get the computer out of the water for a few minutes.
  10. jvogt

    jvogt Solo Diver

    # of Dives: 500 - 999
    Location: Lakewood, CO USA
    I would probably just use ratios. 21% vs 30% is ~13% change in nitrogen. Round to 15% for safety and easy math. Subtract that form your preferred GF High. 70 -15 = 55% GF High. Either program that into your Shearwater or just ride the GF99 data to the surface.
    inquisit likes this.

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