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Mares Horizon - few questions before the decision about course.

Discussion in 'Rebreather Diving' started by Bartlomiej, Mar 29, 2021.

  1. broncobowsher

    broncobowsher Solo Diver

    1,986
    1,464
    If I am reading the question correctly...
    TDI Air Diluent CCR Diver Course gets you into a rebreather. 100' limit, no deco, any problem you bail to air.
    Heliotrox adds Helium to the mix. Adds depth (and not stated, I am pretty sure deco)
    Air Diluent deco should not exist. I am sure it is there for someone who never wants to go deep and have helium, but wants to be down long enough to actually get into deco. The helium card does the same thing. Just run 0% helium in your heliotrox and there you go.

    No Deco Air diluent is often called MOD1, and happens to be 100' limit.
    Heliotrox is often called MOD2, and happens to be a 200' limit.
    There is a MOD3... After that you better know what you are doing as you are on your own.
     
    Zebra 1 likes this.
  2. Wibble

    Wibble Contributor

    # of Dives: 500 - 999
    Location: UK
    764
    529
    The "MOD1" certification doesn't mention deco (IANTD).

    I think that you gain deco certifications through the specific decompression procedures course(s). "MOD1" (in quotes as there's no such thing as MOD1, it's just a name we all use!) certifies you to use the specific CCR unit down to a specified depth (30m/100', 40m/130', 45m/150' with helium) according to your existing qualifications.

    The certification card (certainly IANTD) doesn't mention decompression, only the depth and gas. If you don't have decompression certifications, then MOD1 doesn't bestow it upon you -- which is somewhat difficult if you're diving to 45m as that depth is beyond recreational limits because you're into the 1:1 deco territory - 30mins on the bottom = 30mins of deco (rule of thumb).

    MOD2 - Extended Range - gets you to 60m/200' or 70m/230' using two bailouts (bottom gas and one deco gas). By definition this is a decompression course constrained by bailout gasses. It seems to be equivalent to the "Normoxic trimix / extended range" OC course which too bestows the use of two deco stages in addition to normoxic backgas (>=18% on OC)

    MOD3 is more akin to the OC Advanced Trimix / Hypoxic Trimix which is unlimited depths and unlimited bailout/stage cylinders using hypoxic gas. With a rebreather this would be a lot of team techniques, shared bailout and problem solving.
     
    Zebra 1 likes this.
  3. KenGordon

    KenGordon Rebreather Pilot

    3,898
    2,695
    There are five TDI courses (ignoring deep ER style air)

    Air dil CCR - this is AOW for CCR, 30m no stop. Anyone with deco training (or maybe everyone?) skips this.
    Air dil deco CCR - this is ANDP for CCR 45m with proper deco. Nobody should do this course.
    Helitrox CCR. This is, like Helitrox OC, ANDP with a bit of helium, 35% now, 45m and deco. This is the course to do. It is almost the same as the air dil deco one but with a hour or two of extra academics. I did’t use helium on the course but I was already qualified OC, no idea if that mattered. Everyone should do this course.
    Mixed Gas - 60m trimix - absolutely everyone should do this
    Advanced Mixed Gas - 100m Trimix - more of a minority interest

    On CCR trimix is pretty economical so everyone ought to be doing the Helitrox/Trimix courses. Doing it sooner means quite a lot of diving can take advantage, especially now it is 35% rather than 20 (or was it 25?).

    On my Helitrox course I had to (as a drill) bail out from 32m on air which was the deepest we did on the course that week. I remember noticing the martini effect through that. The last time I used air dil past 30m (38m) in the U.K. I recall taking a very long time sorting out an escaped DSMB. Locally I can get trimix as easily as air so I do.
     
    rjack321 and Zebra 1 like this.
  4. Blackfrogfeet

    Blackfrogfeet Registered

    # of Dives: 500 - 999
    Location: Canada
    35
    32
    I was just talking to an instructor about what courses give you what certs, specifically for IANTD because it is not clear. Apparently CCR Mod 1 is now deco "as required".
     
    Zebra 1 likes this.
  5. broncobowsher

    broncobowsher Solo Diver

    1,986
    1,464
    I actually found it very good. The learning curve is really steep switching to a rebreather. Especially if there has been a lot of time on OC. Just getting in a bunch of recreational dives without getting into multi-stage bailouts and deco is still a HUGE first step.

    It was nice to get some time in and get my act together before adding a second stage, the idea that any problem you just bail and surface. Normoxic Trimix I another step and not a bad one above air DIL.

    Air deco, what is the point? If you already have a basic deco class, nothing really changes. You have your ceiling, plan your bailout for that.

    Helitrox, normoxic trimix, MOD2, that is the area that a rebreather really shines. Helium is useful and economical to use. Good bottom time and good deco.
     
    Zebra 1 and Wibble like this.

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