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Burning the O2 clock

Discussion in 'Advanced Scuba' started by Meister481, Oct 16, 2010.

  1. JahJahwarrior

    JahJahwarrior Solo Diver

    # of Dives: 500 - 999
    Location: West Palm Beach, Fl
    O2 clock or not I have to admit to having a sore throat after a really long hang taking only minimal air breaks. But not enough to make me want to hang longer :)
  2. LiteHedded

    LiteHedded Contributor

    worry less about deco time and more about that o2 exposure.

    I've done some fairly long exposures. never had these symptoms. try lowering that bottom ppo2. I find standard gases and backgas breaks help. as well as going to backgas before a switch for a little cleanup.
  3. ucfdiver

    ucfdiver DIR Practitioner

    # of Dives: 500 - 999
    Location: Orlando, FL
    I wonder how much of this is bottom gas related, and how much is deco gas. If it's CNS clock related, it gets tons worse @ 20ft. The WKPP guys are pushing 1300-1600% or more on the CNS clock, and even at Ginnie I've seen Ainslie push his close to 800%, but I do know he's generous with air breaks during deco.

    Think slowing the ascent to give the lungs time to recover on a very low (backgas) ppo2 before hopping right back on the bottle could play into things here? With a short half life, seems 5-10min recovery @ 30ft would do quite a bit to lower CNS.

    Meister481, what air breaks are you doing to split up the deco?
  4. LiteHedded

    LiteHedded Contributor

    well IMO it adds up. there's no reason to run a high ppo2 on the bottom other than deco weenery. I don't do it. and the guys at wakulla you're referencing don't do it either :p

    it's necessary on deco. it's not during the working portion of the dive. being generous with backgas breaks on the way up goes a long way. and count the breaks as part of the deco. if you're burning your lungs up something is wrong.

    the last trimix dive I did put me at about 160% CNS. no burning throat or lungs.
  5. Meister481

    Meister481 Tech Instructor

    # of Dives: 0 - 24
    Location: Greenwood, Indiana
    That's what I have found to work the best. I don't like using 32 at JB for big dives, Usually end up with 26 or so for a dive like this. Any longer deco and I'll go with a second deco gas. The only reason I posted was for using O2 as the only gas for a dive with this much back gas. It's the limit of such for me. Only fried my lungs once, and got them irritated once. That was enough for me.

    The WKPP dives are well beyond my abilities and knowledge level. Andrew's dives are well beyond me as well. Have a while to go before I get there. Rebreather is the next step in that direction.

    It was definitely BG related, there is no other explanation. Anything under 20 minutes, no breaks, 20-60 minutes 12 on 3 off, over that 12 on 5 off. As far as the slow ascent goes, I do 3 stops in the chimney at JB.

    I'm not going any further with my planning in this thread, I don't need some douche killing himself by using my gas/deco schedule instead of getting trained.

    32 is fine for the short dives, keeps me off the bottle and resting on shore.

    The breaks save you, that's for sure. I upped mine after my issue. No longer happens, ever. Been a long time since I did so.
  6. Cave Diver

    Cave Diver Divemaster

    No problem. I've copied the discussion to a more appropriate venue for anyone wishing to continue the discussion.
  7. LiteHedded

    LiteHedded Contributor

    I think it's shenanigans.
  8. PfcAJ

    PfcAJ Contributor

    # of Dives: 5,000 - ∞
    Location: St Petersburg, Fl
    I break way longer. Anything longer than 20mins on o2 gets a 12 on 6 off cycle, and the stop prior to any gas switch is on backgas.
  9. liuk3

    liuk3 Solo Diver

    # of Dives: 500 - 999
    Location: Los Angeles, CA
    Those of you who have experienced lung or throat discomfort potentially from prolonged exposure for excessive time on oxygen clock, how long of a deco were you doing when it happened? I haven't ever experienced such discomfort and wondering how close my own deco times might be to somebody else's personal experience. I know each person is different in personal physiology.
  10. rjack321

    rjack321 Captain

    # of Dives: 1,000 - 2,499
    Location: Port Orchard, Washington State
    I do 10 on with 5 off for anything longer than 15mins. I generally round O2 time to 5 min increments as well.

    I rarely exceed ppO2 1.2-1.3 on the bottom so backgas breaks on deco are usually a sharp decline in ppO2. I break onto the lowest ppO2 gas I have.

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