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ADV Nitrox and Deco Proc or Helitrox

Discussion in 'SDI/TDI/ERDI' started by mainedvr, Sep 28, 2016.

  1. LandonL

    LandonL ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: I just don't log dives
    Location: Fort Lauderdale, FL
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    Glad you got what you were looking for. You are really going to enjoy it, and welcome to the tech club!
     
  2. DevonDiver

    DevonDiver N/A

    # of Dives: 5,000 - ∞
    Location: Subic Bay, Philippines
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    Consequences.

    Air is far more forgiving of errors than helium. That's why helium was traditionally withheld until later stages, where the tech diver had accumulated more experience and made many of their mistakes.

    If we can assume that training standards are exemplary... and that qualifying divers are mistake-proof straight out of a few days training, then I see no negative issues with introducing helium to the mix.

    Should we assume that training standards are exemplary? LOL
     
    mainedvr likes this.
  3. JohnnyC

    JohnnyC Divemaster

    # of Dives: 1,000 - 2,499
    Location: United States
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    Sure, at hypoxic levels there are serious consequences. At DP/helitrox normoxic levels, hardly.

    On one hand you claim that it's less forgiving and that lax training standards are cause for withholding trimix, yet the standards for each are exactly the same. Same number of hours (6 class), same number of dives (6 w/AN), same depth requirements (2 @ 30m+) and limitations (45m), same standards. They are literally exactly the same course with the addition of helium and some minor lecture to go along with it. So which is it, is TDI wrong and dangerous? Is AN/DP inherently safer? And if so, how does TDI get away with justifying teaching trimix at the same level?

    I highly doubt TDI would be willing to risk the liability of putting the same AN/DP students on mixed gas if it was actually an issue. Which, considering all else being equal, why even bother requiring another course if you're willing to trust AN/DP caliber students with breathing helium. If it were that dire, they wouldn't have the same standards.

    I'm not a GUE nut hugger, but getting on helium sooner isn't more dangerous. Feel free to check the standards for yourself.

    https://www.tdisdi.com/wp-content/uploads/files/sandp/currentYear/TDI/part 2/pdf/individual/TDI Diver Standards_10_Helitrox_Diver.pdf

    https://www.tdisdi.com/wp-content/uploads/files/sandp/currentYear/TDI/part 2/pdf/individual/TDI Diver Standards_08_Decompression_Procedures_Diver.pdf

    I also apologize for threadjacking in the agency Q&A area, I got here through the recent posts link.
     
    Last edited: Sep 28, 2016
  4. DevonDiver

    DevonDiver N/A

    # of Dives: 5,000 - ∞
    Location: Subic Bay, Philippines
    15,396
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    I don't particularly care what the standards say... for most agencies, including TDI. I see technical divers, day-in, day-out, visiting from around the globe and holding a myriad of agency cards.... and there's obviously some very low interpretations of training standards judging by some of the diving I see performed.

    I don't have a problem with GUE's approach...or attitude to helium use. But.... THEY have a fundamentals program which ensures students enter training with sufficient baseline skill from which to develop appropriately on the course.

    In contrast, TDI... and most other agencies...do not have such a system. They'll let recreational advanced divers onto the program with 50 dives experience.

    4 technical training dives.... seriously.... from relatively novice recreational diver to using helium at 45m.... THAT is my issue. It's quite a big stinking issue.

    So yeah.... more tech agencies wanna ride the 'helium' bandwagon, but they don't want to pay the conductor (by adding a rigorous pre-course assessment system).

    If you don't see a difference in the precision needed between diving air and trimix, then you're missing something critical in your understanding. As for mix %... how much saturated gas do you need to form a tiny bubble that has big physiological effects?

    20% at 45m is still ppHe1.1... and we're not talking about no-stop rec dives...so that's plenty enough to bubble.... much quicker than nitrogen. It's the speed of helium that causes issues... it's a fast gas. Fast to saturate, fast to supersaturate....and fast to bend.

    Missed stop? ​
    BOOM​

    Omitted deco? ​
    BOOM​

    Fast ascent? ​
    BOOM​

    Imprecise stop buoyancy? ​
    BOOM​

    Those occasional mistakes you'd make as a novice technical diver.... the ones you'd probably 'get away with' on air.... now.... on helium mix.... you won't get away with... not once.

    There's nil liability to TDI. They have agency standards...and the liability switches to instructors at the risk management/student assessment level by applying those standards (or not) appropriately. So they'll add helium in basic entry-level tech... and it's fine... so long as chamber statistics don't rise sufficiently to necessitate discrete back-tracking later on.

    But I do want to get this straight... I am not disputing that any agency shouldn't offer normoxic trimix training in lieu of air for dives in the 4-6 atm range. I am merely answering the question you asked: "Tell me what issues you think a diver would have running normoxic trimix as opposed to straight air or nitrox for any of the actual dives for AN/DP".

    To answer your question (again)... the issue is that there are more consequences to making mistakes on helium than with air. You get bent quicker, for smaller discrepancies in ascent behavior. A paltry 4 dives of technical level training is not significant for producing divers who need a significantly higher insurance against mistakes.
     
    Last edited: Sep 29, 2016
  5. USMC CPL.

    USMC CPL. Barracuda

    # of Dives: I'm a Fish!
    Location: Lake Havasu city
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    I am hoping to start an/dp soon and was wondering if intro to tec was required or if it was up to the instructor. Thanks neil
     
  6. Marie13

    Marie13 Great Lakes Mermaid ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Great Lakes
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    Read the standards for yourself.

    https://www.tdisdi.com/wp-content/u... Diver Standards_07_Advanced_Nitrox_Diver.pdf

    https://www.tdisdi.com/wp-content/u...andards_08_Decompression_Procedures_Diver.pdf

    https://www.tdisdi.com/wp-content/u...DI Diver Standards_03_Intro_to_Tech_Diver.pdf


    I guess it would depend on where your skills currently are. Do you NEED intro to tech?
     
  7. decompression

    decompression Instructor...seriously...

    # of Dives: 5,000 - ∞
    Location: Victoria, BC, Canada
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    Required no, but might be recommended by your instructor. If you're just over the minimum req's and have little/no deep or doubles experience the intro to tech course is a good foundation for the AN/DP course.
     
  8. Marie13

    Marie13 Great Lakes Mermaid ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Great Lakes
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    Are you required to take Intro to Tech in doubles (SM or BM)? The standards weren't really clear on that to me. I'm thinking about doing it late next year or the following year, but that timing would be changed if I had to get into SM first.
     
  9. elgoog

    elgoog DIR Practitioner

    # of Dives: 200 - 499
    Location: San Francisco Bay area
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    You can do Intro to Tech in single tank - it was one of the courses my wife and I were looking at along with Essentials, Fundies, etc when we were just starting off diving more regularly.
    Also, if you do decide to do AN/DP/H, the instructor at that time may just need to see you in the water with the doubles setup (BM or SM) and that would be it since ITT isn't a pre-req for any courses higher up the ladder.
     
  10. Marie13

    Marie13 Great Lakes Mermaid ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Great Lakes
    5,429
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    Thank you. That's very helpful. I was planning on taking the TDI SM class anyway.
     

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