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Do you lie about your helium content?

Discussion in 'Rebreather Diving' started by rddvet, Nov 25, 2019.

  1. rddvet

    rddvet DIR Practitioner

    # of Dives: 50 - 99
    Location: Florida
    I've got OC ART, so when I moved to CC I was able to be taught with helium in the diluent. I generally dive 30/30 for most things, since the deepest dives I'm currently doing are Ginnie and Little River and I'm just trying to keep a lower END. I will occassionally dive 21/35, but 30/30 has been in my tanks for a while and that's what I've been sticking with.

    I've been surprised lately by how many people have told me lie to my shearwater and not input the helium in order to avoid the helium penalty. Most have strongly suggested to just "pad the deco a little". This was discussed in my ART course, but it was decided that a little extra deco due to helium penalization isn't a bad thing because I've had 2 minor skin bends incidents.

    I'm just a little surprised how many people have been adamant about lying to their computer. Is this way more common than I realize? I've done the math and have seen that the difference in deco between 30/30 and 32% isn't hugely significant.
  2. Gareth J

    Gareth J Manta Ray

    # of Dives: 1,000 - 2,499
    Location: UK
    I've always worked on the basis, that I little extra deco is better than a trip to the chamber.
    Not to mention the potential unknown issues of long term damage that one might be experiencing with non symptomatic dci.

    I don't see the point of not putting the true gas into the computer. If you wish to be 'aggressive' with your decompression you can change the gradient factors, after all, that's what they are there for!
  3. Wookie

    Wookie Secret Field Agent ScubaBoard Business Sponsor

    No. I have been bent (skin, mostly) multiple times, but never when following trimix protocols on my shearwater. I don't see any need to push what I consider recreational limits. I mostly get bent on commercial dives, where I'm being well paid. I don't need to get bent when I'm having fun....
  4. grantctobin

    grantctobin Solo Diver

    # of Dives: 500 - 999
    Location: Chicago
  5. rjack321

    rjack321 Captain

    # of Dives: 1,000 - 2,499
    Location: Port Orchard, WA
    I always viewed the lying about He% as a holdover from early trimix computers like the NiteckHe. In all fairness people lie to their sunnto in various ways to avoid 2nd recreational dive NDL penalties too.

    I don't lie to my shearwaters and how I feel post dive seems to be strongly correlated with my GFhigh and whether its the 1st or 2nd dive of the day. Maybe its all psychosomatic but seems to be working way better than past approaches which "worked" but were pretty aggressive at the time.
    grantctobin likes this.
  6. wedivebc

    wedivebc CCR Instructor ScubaBoard Supporter

    The difference in deco using a CCR between 21/35 and 30/30 would be minuscule. For fudging other mixes it makes no sense either. You use a computer to give you a real time reality check. Presumably when you go on a technical dive you already a sense of time. depth and ascent profile and the computer just is there to give you a reality check. There are so many ways to fudge the deco profile but I would think lying about the helium content would be the least reliable.
    Spend an hour with your favourite deco planner and see what effect different changes make.
  7. nickbutcher

    nickbutcher Angel Fish

    I don't call it lying but I don't dial-in the exact numbers. I have a set of gases in my JJ Petrel and just pick the next lowest helium %age to whatever diluent I get. So, if I get 18/36 for instance, I'll select 18/30 'cos that's one of the mixes I have in the list.

    I don't sweat too much about the correct O2 %age either. I don't have a BOV, so I'm not gonna be breathing the diluent OC. Just pick the nearest mix to whatever I end-up with.
  8. broncobowsher

    broncobowsher Solo Diver

    garbage in, garbage out. At that point why are you using a computer. cut some tables and go off a depth gauge and a bottom timer.

    No reason to lie to a Shearwater.
    TrimixToo likes this.
  9. nickbutcher

    nickbutcher Angel Fish

    The 'reason' would be to minimise unnecessary decompression, if one believes that helium is no different to nitrogen in terms of deco obligation.

    I think that there is probably a lot of mileage in this theory but I am not in that much of a rush to get out of the water that I'm prepared to try it. Many people are and seem to be doing OK on it.
  10. cerich

    cerich ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 5,000 - ∞
    Location: Georgia
    my dad once said, don't lie to your doctor, lawyer or accountant because they are the ones that need the truth to keep you out of trouble or get you out of it.

    I extend that to a dive computer.

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