OC to CCR: After Trimix? Or after Adv Trimix?

[stuartv]

I've read and searched and I don't really see my specific question addressed.

I'm starting TDI Trimix training and expect to be done with it before the end of this year. My plan, up until now, has been to build experience doing normoxic trimix dives over the next year and then do TDI Adv Trimix training at the end of next year. Then, at some point after that, move on to diving CCR.

My thought has been that I want to be a somewhat experienced and proficient hypoxic trimix diver before moving on to CCR.

My long-term goal is to dive the Monitor and other deep wrecks.

So, I'd say my goal would be to be done with MOD 3 CCR training in 3 to 4 years.

Lately, I've been starting to wonder if the increment in skills that I would gain by undertaking Adv Trimix training on OC is a good way to spend my time. Would I be a better, safer MOD 3 CCR diver in 4 years if I continue with my plan to get experience in Adv Trimix, on OC, before moving to CCR? Or will I be a better, safer MOD 3 CCR diver in 4 years if I do Trimix, get some experience on OC Trimix (normoxic) to develop my skills to real proficiency (i.e. not just "get the C card" proficiency), and then move to CCR straightaway?

I know there are some people who would say to move to CCR immediately, if that's my long-term goal. I don't want to do that. I want to feel like I am comfortable and proficient at managing multiple deco cylinders on a deep(-ish) OC dive before I add CCR complexity to my life. Also, even though I know it's a whole different ball game, I want to improve my basic diving skills (on OC) more before I make the change. Like I said, I know buoyancy is a different beast on CCR, but I will feel better learning CCR if I know that my buoyancy is better on OC, in the event I have to bail out and finish a dive on OC.

So, I'm mostly interested in hearing from the people who advocate OC proficiency first, before moving to CCR. Do you think it's really worth the extra time to go from Trimix to Adv Trimix on OC before going to CCR?

Related question: If I switch to CCR after Trimix, and then advance to the MOD 3 level, does the MOD 3 CCR certification make me "certified" to do hypoxic trimix OC dives? Or does it only certify me to use hypoxic trimix as a diluent and bailout gas, but I would not actually be certified to do a complete hypoxic trimix dive on OC alone?

This may actually resolve the issue for me. I would want to have the certification to be "able" to do hypoxic trimix dives on OC, if the opportunity presented itself and OC was the only option for doing the dive. So, if MOD 3 CCR doesn't give me that certification, I suppose I would press on to get the Adv Trimix OC card, regardless.

 

[tstormdiver]

I am doing my Normoxic Trimix on my Prism2. Really the only gas knowledge needed to learn closed circuit rebreathers, is a good understanding of Nitrox.

 

[KevinNM]

The argument I got from a CCR diver was that when you bail out you are an OC diver. And after a failure is a pretty terrible time to learn how to do a long oc deco ascent.

 

[stuartv]

The argument I got from a CCR diver was that when you bail out you are an OC diver. And after a failure is a pretty terrible time to learn how to do a long oc deco ascent.

Right. That's why I'm doing at least normoxic trimix and getting some experience with that before CCR. The question is whether I need to do hypoxic trimix and get experience with that before starting CCR.

I'm already doing what seems like long OC deco ascents now. Last weekend, one dive was 1:42. 47 minutes or so of bottom time (around 140') and then almost an hour of deco on 80% (only being currently trained for 1 deco gas kinda sucks, but I'm fixing that now). I know it's not LONG deco, by the standards of a bunch of people here, but it seems long enough that another year or so of diving like that (but with 2 deco gases, starting fairly soon) might be sufficient experience with OC deco to think about moving to CCR.

 

[ffdiver]

I don't personally buy into the "you are now an OC diver" once you bailout. You still have a CCR on your back that you need to deal with and there are far more options available to you rather than just go OC. You can't learn to do CCR bailouts and manage those perfectly without CCR experience and training.

I say go CCR as soon as you can and learn the way you plan on diving.

 

[northernone]

If we have respect for the advisors for the various certifying agencies we would need to recognize the industry standard is trimix OC bailout drills are viewed as part of trimix CCR training not as a prerequisite.


It's easy to feel safer by 'exceeding minimum standards' by doing more OC training/experience but I feel there is historic caution from the many dead experienced TRIMIX OC divers who began diving CCR and progressed too quickly based on their OC experience (a tentative analysis) . I'd hold the current consensus by the training agencies is a safer progression with a slow progression CCR diving and training. An extra hour CCR training makes you a better CCR diver than an extra hour OC training.

In summary I think being experienced adv trimix OC may increase your risks as a CCR diver compared to investing in more CCR training and hours.

I did the OC route before CCR but feel I'd be a better CCR diver now if I had switched to CCR a decade ago.

Interesting discussion topic.
Cameron

 

[Tug]

I made the switch after taking a trimix class and I'm glad I did it that way. It gave me some experience with gas switches involving multiple bottles which was helpful during my rebreather class. I don't think it's necessary but if you're taking the class already it'll be nice.

An added bonus is you can use trimix in your diluent bottles

 

[tstormdiver]

The argument I got from a CCR diver was that when you bail out you are an OC diver. And after a failure is a pretty terrible time to learn how to do a long oc deco ascent.

I guess I got "On- The- Job- Training" during the start of my Normoxic course. I lost my loop mouthpiece (it came off) within moments of arriving at 200 ft on my first Trimix dive. I shut down the rebreather & bailed out successfully to the correct OC mix, with no problems & completed my OC deco in the Cozumel currents with no real issues (I'm a quarry rat, so not as confident about currents). Was I excited/ concerned? Yes,... it took a little bit to get my breathing back to normal, but it was more of an inconvenience, than anything, in the end. I practice OC bailout & simulated deco & diluent flushes, quite a bit ,in the local quarry. By the time I started my basic CCR training, I was already Adv. Nitrox / Deco & Full Cave, Cave DPV & multi stage certified, so doing Deco on OC was no big deal.

 

[DevonDiver]

I've always believed in the moniker "train how you'll fight". In diving terms, that means to keep your training as relevant and realistic to the diving you plan to conduct. I see little point pursuing OC Advanced Trimix if your goal is CCR Trimix. You'd be better off starting earlier building up your hours on your unit.

 

[PfcAJ]

Master oc technical diving. Multiple bottle management, gas switching, dive planning. Then add in the rebreather. When it breaks you need to be a strong oc diver, there's a fair chance that you'll be mentally compromised in some way if that RB breaks.