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Accumulated 02 following a large number of repetitive Nitrox dives over 3 days.

Discussion in 'Advanced Scuba Discussions' started by Astran, Sep 30, 2019.

  1. BRT

    BRT Giant Squid

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    They were not at 1.6 PPO2. They were a little over 1.0.
     
  2. Astran

    Astran Banned

    # of Dives: 200 - 499
    Location: MD
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    Hopefully @scubadada can weigh in on this, but I'm going to wager a guess that his other computer, the less conservative one, tells him to end his dive due to reaching 02 limits.. probably never.

    That's quite different from using 2 computers with different algorithms to determine a favorable NDL bottom time.
     
  3. scubadada

    scubadada Diver Staff Member ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Philadelphia and Boynton Beach
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    Correct, neither my Nitek Q or, now, my Teric, has ever gotten close to daily O2 exposure.

    The Oceanic computers display the lowest of the values between NDL, O2 exposure, or air time remaining, if air integrated, as the dive time remaining on the main screen. These carry labels, Air, NDL, O2, to let you know which one is controlling the dive. When you exceed the O2 limit, the dive time will register 0, as it did for @Astran . The NDL and/or air time remaining can still be found on alternate screens and/or bar graphs. It is easily possible to continue diving safely, within NDL, after reaching the O2 limit. It sounds to me, that is what Astran and buddy did.
     
  4. rhwestfall

    rhwestfall Solo Diver

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    Not convinced that you should be using that word (red/bold above).... Though not something immediately apparent like convulsion, the potential injury is real (and seems to be unpredictable)... Again, always pushing to the limits is a questionable practice.

    Although, this is just my opinion.


    YMMV
     
    markmud likes this.
  5. LiteWeight

    LiteWeight Solo Diver

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    Location: Bonaire
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    You don't need a computer. I've performed many dives to 200' with no computer.
     
    Astran likes this.
  6. tursiops

    tursiops Marine Scientist and Master Instructor ScubaBoard Supporter

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    Hey, tell the rest if the story! Air? Single tank?
     
    markmud and peocro like this.
  7. kmarks

    kmarks Divemaster

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    We don't know exactly what ppO2 he was at throughout the dive because even a square profile isn't actually square, but you're right, he was never actually at the ppO2 1.6 that he was allowing himself to reach. I only mentioned that as an example because he said that he had accepted the risk of setting his computer's alarms to go off at ppO2 of 1.6 and I was pointing out that whatever ppO2 you are currently experiencing, it makes a difference on your CNS clock time, and if you were to dive the clock time tables (as opposed to using a computer), you have to assume a square profile, just like diving on the more familiar NDL tables.
     
  8. dmaziuk

    dmaziuk Orca

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    PO2 is only relevant if you're riding the limit all the time. What Leo manual doesn't say is whether it's using the "rolling window" or "half time" method to draw that little O2 toxicity bar graph. In fact I'd say its manual is actively misleading on the subject.
     
  9. Astran

    Astran Banned

    # of Dives: 200 - 499
    Location: MD
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    Because, well you know, I sometimes use it for other stuff that I think is more important [than ultraconservative max 02 settings that can be safely ignored], such as NDL limits, gas supply remaining, elapsed dive time, depth, ascent rate, that sort of thing.

    Why did I ignore my computers 02 alarms given that both of my computers and my buddies computer all indicated violations?

    Because it just didn't seem right. Because we were at about 60' at the time. Because I didn't think our dive profiles were all that much different than dives I've done 100s of times before. That's all I got..

    Although it was a somewhat impulsive decision it appears to have been the correct one given the information provided on this thread primarily by @scubadada.
     
  10. rjack321

    rjack321 Captain

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    Location: Port Orchard, WA
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    Huh?
    They weren't at 1.6 but almost all the dives were over 1.2 and closer to 1.4
    109ft on EAN32 is ppO2 1.37
    96ft on EAN36 is ppO2 1.4
     
    markmud likes this.

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