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Deep Air Diving - thoughts

Discussion in 'Technical Diving Specialties' started by Daylonious, Jun 20, 2008.

  1. Thalassamania

    Thalassamania Diving Polymath ScubaBoard Supporter

    # of Dives: 5,000 - ∞
    Location: On a large pile of smokin' A'a, the most isolated
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    My problem is with the word "considerable." Higher, increased, greater, etc. would be fine but "considerable?" Naw.

    They twitched, dropped the BIBS mask, and and that was that.

    No, first time was as I a youngster peripherally involved in a sea otter TV show in the mid '60s, then later, as a graduate student and later still as the DSO for an oceanographic institution.
     
  2. Air One

    Air One Solo Diver

    # of Dives: 500 - 999
    Location: Normandy-France
    454
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    Yes.
    And of course I would respect the run time during the way up, or the deco on my computer. You surface as fast as you can.
    But I did not loose my buddy.

    What do you do when you loose your buddy ? You wait for him ? You search on the bottom ? In that case, how long ?

    Or maybe you thought I meant I'd immediately surface ?
     
  3. rjack321

    rjack321 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Port Orchard, WA
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    She overstayed her planned bottomtime by 2x and still failed to ascend and start her deco (supposedly due to perceptual narrowing and narcosis). Being rediculously under equipped for the dive didn't help matters. I'm sure there are plenty of other stories of people who "felt fine" until things started to go sideways with deep ENDs.

    Personally I would do (haven't actually needed to) air or weak nitrox to 120-130ft. Beyond that I'm not really interested. Considering I'll only remember 1/2 of it, why bother. I also don't attempt to drink precisely enough beer to get my BAC to 0.079 so I can still drive home legally (impaired but legal).
     
  4. SparticleBrane

    SparticleBrane DIR Practitioner

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    For those talking about doing a chamber dive to see the effects of deep air:

     
  5. DA Aquamaster

    DA Aquamaster Directional Toast ScubaBoard Supporter

    # of Dives: 2,500 - 4,999
    Location: NC
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    I worked as a police officer while I attended college and I read the state wide BAC printouts every morning. At the time .01 was the legal limit. To put it in perspective, most people become severely impaired in terms fo both judgment and coordination at .15, are at risk of blacking out and passing out at .20, will be unconcious at .30 and will be at high risk of dying to to respiratory arrest at 40. However, it was common to see people with BAC's in the .30 to .50 range, who were not only awake but actually driving a car with at least some degree of success with BAC's that shoudl have killed them.

    These were individuals who were seriously alcoholic and who functioned "normally" at BAC's that would leave a non drinker on the floor, and in fact when sober they were so neurologically impaired by DT's that they probably could not drive at all.

    So in effect, if we want to insist on the alcohol impairment analogy, we have to be willing to accept the possibility that narcosis does not affect all divers equally, that some divers may have more resources than others to start with and can in effect stand to lose more to narcosis than other divers and still be effective to the required degree, and that divers who dive deep air a lot may in fact develop a degree of tolerance.

    I'm not saying any of the above is neccesarily true or false, but I am saying if anyone wants to use alchol impairment as an analogy, they had better be willing to look at both sides of the issue.


    -------


    For long exposures, PO2's in the 1.2 to 1,4 range are preferred as the risks associated with them are very low. 1.6 is considered ok for deco by most agencies as the work load is quite low and the benefits offset the risks. But in the now distant past 1.6 was considered ok for bottom gas.

    In effect, the higher the PO2, the shorter the allowable exposure time, but 1.6 is by no means the maximum that can be tolerated with a reasonable degree of safety - it is just that PO2;s above 1.6 are not considered acceptable for long exposures.

    The US Navy developed short term O2 exposure charts that allow high PO2 for short periods of time - as in 2.0 and above for very short periods in the 5 to 10 minute range. Deep air records in the 400 ft range have also been done with what are considered to be very high PO2's (the 2.8 range) but on very short profiles with minimum time above 1.6.

    During WWII the British did research on rebreathers and routinely had divers at 50' on 100% O2 for in excess of 10 minutes (PO2 of 2.5).

    So in light of what's been done, an ascent from 150' to a 70' stop for the couple minutes it would take to get there poses no excessive concern for oxtox as the exposure is short. It is not ideal, but if it's all you got, it's all you got (which is a bigger issue you need to beat yourself for later.)
     
  6. MaxBottomtime

    MaxBottomtime Divemaster

    # of Dives: 1,000 - 2,499
    Location: Torrance, CA
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    I have a question for those who say they can't remember what they saw when diving deep air. I have more than a dozen 200' dives on air and about 100 deeper than 150'. I've never once forgotten any portion of a dive nor any detail about the animals I looked at. Are you getting so narced that you are barely able to function? Whenever I've felt narced I have always ascended or aborted the dives. If the narcosis was caused by CO2 buildup from swimming too fast or moving the anchor I've stopped, taken a couple long breaths and it went away. On the trimix dives I've made the difference was noticable, but not enough to make me want to pay for helium each time I dive deep.
     
  7. Thalassamania

    Thalassamania Diving Polymath ScubaBoard Supporter

    # of Dives: 5,000 - ∞
    Location: On a large pile of smokin' A'a, the most isolated
    22,171
    2,771
    113
    I've made 100s of dives between 150 and 190 and (as far as I can remember) I've never forgotten anything about the dives.
     
  8. drbill

    drbill The Lorax for the Kelp Forest Scuba Legend

    # of Dives: 2,500 - 4,999
    Location: Santa Catalina Island, CA
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    Likewise, I've done a number of dives on air to 180 to 200 ft and remember what I saw despite the fact the total dive time might be 50-60 minutes (deep stops plus a long shallow deco). What I don't remember is why I wanted to surface! Just so no one thinks I've got some incredible SAC rate, when I did these dives I was diving on an HP120 (although only filled to about 100 cu ft most of the time). I don't do them now since I no longer have that tank. My max O-2 exposure was never over 5% by the end of the dive.

    Was I narc'ed? Certainly I could sense the effects of narcosis, but nothing that prevented me from locating, framing and following video subjects.
     
  9. Air One

    Air One Solo Diver

    # of Dives: 500 - 999
    Location: Normandy-France
    454
    5
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    To be sure that you remember everything, you have to do memory exercises on the bottom and check when you surface. You also have to do those exercises with a Tx diver who would describe your reactions, and the time you take before to react.
    I have a very big doubt about the feeling we have after those dives.
     
    Last edited: Jun 25, 2008
  10. Xizang

    Xizang Tech Instructor

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    can this be compared to elite alpinists who summit everest without bottle oxygen vs with bottle oxygen? Is climbing everest without oxygen also considered reckless and unnecessary?
     

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