Is it worth to do OC trimix before CCR Helitrox?

[J-Vo]

What are you defining as "trimix"?

I do 270' dives fairly regularly. I need 4 AL80s for bailout to do any appreciable bottom time. Even at 200' (normoxic) dive requires 3 AL80s. Add any penetration and you need an additional cylinder or more of bottom mix.

Someone coming from AN/DP were they only had doubles and a single 40 is going to be overwhelmed with a breather + 2 bailout bottles (for Helitrox). If your already practiced with several s80 stage/deco bottles the bailouts are no longer adding to the new task load and you can concentrate on flying the unit.

 

[BlueTrin]

What are you defining as "trimix"?

I do 270' dives fairly regularly. I need 4 AL80s for bailout to do any appreciable bottom time. Even at 200' (normoxic) dive requires 3 AL80s. Add any penetration and you need an additional cylinder or more of bottom mix.

Someone coming from AN/DP were they only had doubles and a single 40 is going to be overwhelmed with a breather + 2 bailout bottles (for Helitrox). If your already practiced with several s80 stage/deco bottles the bailouts are no longer adding to the new task load and you can concentrate on flying the unit.

I meant the first trimix cert, TDI Trimix Diver - International Training - SDI | TDI | ERDI | PFI

I saw you mentioned multiple stages, I’ll definitely mention this as a concern to the instructor.

 

[J-Vo]

I meant the first trimix cert, TDI Trimix Diver - International Training - SDI | TDI | ERDI | PFI

I saw you mentioned multiple stages, I’ll definitely mention this as a concern to the instructor.

I believe the standard for TDI Trimix is two deco gasses. You don't get 3 until Full Trimix. My full Trimix required proficiency with 4 stage/deco bottles, but we only used 3 on the "real" dives.

My comment was regarding mostly going directly to CCR from AN/DP were you normally have only used a single 40 deco bottle.

 

[Whitrzac]

No, you can go right from AN/DP to CCR helitrox(150ft max).
0 reason to do OC trimix first and about 2000 not too.

 

[DanFromDownUnder]

Are you already certified on a rebreather ? if not your probably going to be tooling around for many hours above 90ft anyway. I did my cert for my JJ then went back a year later and did full cave and trimix at the same time. It was a steep learning curve but a lot cheaper on the gas costs.

 

[broncobowsher]

AN/DP to rebreather. That is the path I took. The first year was air DIL and no deco. Which for transitioning to a rebreather was good. Wasn't the strongest tech diver coming into this. Lot of learning.

Year later it was time to actually get the Normoxic deco so I could get the use out of the rebreather I was after. First time on Helium in the water. Instructor had no issues and this was normal for him. There was enough instruction regarding Helium in OC in that class I am comfortable with it. Doesn't mean I am planning an OC trimix dive, but I can plan a CCR dive with bailout.

I am going to say take a pass on the OC trimix class. But do have a talk with the CCR instructor before hand. Maybe they really want you to come into the CCR with a trimix background. Or maybe they will just take care of it when you take the class.

If you were not already expecting it, you are not starting your rebreather path on Helium. Take the air Diluant class with 100-150' limits and go have fun the fist year or so. Then go take the Helium.

But really, have a talk with the CCR instructor on what they want to do

 

[kierentec]

I just taught a Helitrox class. I'm assuming it will be my last one. The amount of He in the mix is close to being inconsequential (END of 113 on a 150' dive, at best), but more importantly getting He for open circuit is basically a non-starter at this point. Even if I can get it for class, the students won't be able to get it to conduct dives. They'll be stuck doing 150' dives on air, which they wouldn't have done before.

Just go CCR. It will change your diving point of reference so much, that mix before or after doesn't really matter. Getting on the loop sooner than later is more important than if you have a mouse fart of He in your mix or not. I just did a CCR course for a Prism, cross over for me, first CCR for the other three students. It was an air dil class, even though all three of them are mix certified on OC, and I'm normoxic CCR.

21/35 has an END of 86ft at 150...and significantly lower gas density than air or nitrox (really the biggest benefit for dives in that range)

 

[DiveTucson]

As you mentioned you can go directly from AN/DP to the CCR. Based on the AN/DP background you / your instructor essentially have 3 choices within TDI at least.

-Air Dil No Deco 100’ limit
-Air Dil Deco 130’ limit I believe (I personally don’t/won’t teach this course)
-Helitrox 150’ limit

I frequently take students this way. If you want to to take the 150’ course we will give it a shot. Some peoples skills are adequate and they have enough experience at the AN/DP level where they can handle the task loading on the CCR to execute deco dives to 150’ out of the gate.

Some students do not. What happens semi-regularly is the student starts with the goal of Helitrox and ends up leaving with Air Dil No Deco until they have enough time on the unit at 100’ to complete the 150’ upgrade to Helitrox.

Every diver is different and develops and different speeds. A candid and honest conversation with your instructor will get you a long way. Lots of strange advice in this thread from folks that I am guessing are not CCR instructors. My .02 cents as an active CCR instructor on two different units.

 

[rddvet]

IMO opinion and the opinion of the instructors I respect the most, learn OC trimix. When you have to bail out you're going to be OC. You need to learn proper bottle switches and what not. You can learn that in cc, but I think learning it in OC is best. The only caveat to that is if there is absolutely no way for you to get access to big helium fills, then do it ccr. I'm helitrox certified on my ccr as my mod 1 basically since I was already helitrox oc. I'll be finishing up Tech 1 in a few months (I needed to work on some things before finishing) and I specifically am taking it because I plan to do some more advanced CCR OW deco dives and want the best skills possible, which tech 1 will give me. I will likely take Tech 2 eventually as well. I have 0% likelihood of taking any ccr specific trimix classes. I see no point after taking OC trimix classes.

 

[DiveTucson]

IMO opinion and the opinion of the instructors I respect the most, learn OC trimix. When you have to bail out you're going to be OC. You need to learn proper bottle switches and what not. You can learn that in cc, but I think learning it in OC is best. The only caveat to that is if there is absolutely no way for you to get access to big helium fills, then do it ccr. I'm helitrox certified on my ccr as my mod 1 basically since I was already helitrox oc. I'll be finishing up Tech 1 in a few months (I needed to work on some things before finishing) and I specifically am taking it because I plan to do some more advanced CCR OW deco dives and want the best skills possible, which tech 1 will give me. I will likely take Tech 2 eventually as well. I have 0% likelihood of taking any ccr specific trimix classes. I see no point after taking OC trimix classes.

I’ll leave this as you don’t know what you don’t know. There is massive value in say a Hypoxic CCR course due to stuff that is not covered in an OC Hypoxic course.