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Gas mix

Discussion in 'SDI/TDI/ERDI' started by stevensamler, Oct 27, 2019.

  1. VE7DAC

    VE7DAC Regular of the Pub

    # of Dives: 100 - 199
    Location: Victoria BC Canada
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    My AN/DP course (one dive left) has all been air backgas. If you dive the best nitrox mix for a given depth, you won't have a lot of deco to do. Which is normally a good thing, but not so much when you want to get practice with actual deco. Plus air is cheap/free depending on the deal with your shop (I've got a yearly fill card) while O2 has an associated cost.
     
  2. Mark Powell

    Mark Powell Scuba Media & Publications

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    Yes for Deco Procedures but for this range I would normally recommend Helitrox which covers the use of up to 35% Helium for dives to 45m. Using Helium greatly reduces the gas density and END for deep dives.
     
  3. Marie13

    Marie13 Great Lakes Mermaid ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Great Lakes
    5,590
    3,939
    113
    @Mark Powell

    TDI needs to update its website. There’s conflicting info for Helitrox for helium percentage. The brief info about the course mentions mixes with no more than 20% helium. However, the standards actually mention up to 35% helium. Screen shots below. This caught my attention as I’m signed up for AN/DP/Helitrox next year with all bookwork completed.

    I’ve had 20% helium maximum on the brain. Did the percentage recently change?

    4BD40519-7E6D-44E4-A86B-87BC63825244.jpeg 9AEA8D39-2289-4085-A039-C77071AD833A.jpeg
     
  4. grantctobin

    grantctobin Solo Diver

    # of Dives: 500 - 999
    Location: Chicago
    166
    34
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    The numbers in the footer correspond to a MMYY. The newest standards were published within the past month.
     
  5. kierentec

    kierentec Captain

    # of Dives: 5,000 - ∞
    Location: High Springs, FL; Tulum, Mexico
    369
    205
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    This standard was just changed for the 2020 standards. The maximum helium percentage is now 35%. The course description just has not been updated on the website yet.

     
    kensuf likes this.
  6. Marie13

    Marie13 Great Lakes Mermaid ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Great Lakes
    5,590
    3,939
    113
    That explains the discrepancy, then. Thank you!

    ETA: I just completed the Trimix book last week and so this is an interesting change. A friend is loaning me a suit bottle and rigging kit. Just need to add a hose and OPV to an extra first stage I have.
     
    kierentec likes this.
  7. KentB

    KentB Barracuda

    # of Dives: 200 - 499
    Location: Vancouver
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    i did AN/DP and ER as sort of 1 long combined course, the first couple dives we did were skills dives on a local shipwreck theres a good spot with a railing all the way around to use as a reference for buoyancy during skills and its was 55-65' feet and max depth we got to was around 100 on those so we used air or 32% and 50% he didn't care what we used as long as we were within the MOD and we both used the same gas with same plan. the deeper dives we used air and 50%, with the last 5 i think? maybe 6 dives we were using air,50%,and o2



    Its a fantastic course have fun!

    TDI doesn't use standard gases like GUE does so its dependant on planned depth
     
  8. Mark Powell

    Mark Powell Scuba Media & Publications

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    Thanks for spotting that. As the others have said that only just changed in the standards. I have emailed the website team to remind them that the course description also needs to be updated.
     
    Marie13 likes this.

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