Trimix Qualifications on YBOD? Should I?

[DecoWarrior]

at the end of the day do what you are comfortable with, some people are not happy doing things off their own back, i was and others have been find what suits you and do it, you dont have to tow the party line!!!,

[Mdemon]

I like this bit best:

I also have the benefit of probably more theoretical knowledge than most, and access to manufacturers & test houses, as I look after the UK navy's rebreathers for a living.

Don't be such a bloody tart

I'd be willing to risk buddying with you as a narcosis benchmark but I seem to give the impression of being narked on anything over 5m

Daz

P.S I reckon with your enquiring mind and background you will be pretty much ok on the self learning route.

[PrettyFishies]

Hi Mary

There are two schools of thought on CCR trimix, one is that training is critical the other is that there's nothing new in adding He as it's just gas physics. The gas side is a no-brainer, the more important factors come into play when planning logistics of deep dives and working out bailout gases for "what-if" scenarios.

I am of the school of self-teaching although I am extremely selective with regards to what advice I take on board and whom I believe to be credible sources of that advice. There is a lot of bullshit propogated about CCR. Experience is a great teacher.

Using air below 40m on CCR does precipitate quite extreme narcosis, particularly on fast descents. Also the CO2 gradient in closed loop is completely different to open, CO2 can actually be narcotic on fast descents so it's a double whammy with N2 in CCR.

Narcosis on CCR can be significant at depths where OC air would not present the same level of narcosis. For this reason alone, I am an advocate of using mix in the CCR below 30-40m, I've dived to 55m on air CCR and 100+ on mix CCR, I was very narked on air. Through many experiences in CCR diving, I believe that anything which intereferes with the ability to recognise changing/impending physiological signs and symptoms is extremely dangerous. This is particularly valid in the context of the divers who get happy and fluffy with narcosis - I am definitely a "raptures of the deep" type of diver and without mix I'd never have a clue if I had CO2 or another physiological problem.

The Mod 1 course gets around this by only certifying divers to 40m on air diluent. So any "further education" which a diver gains regarding equipment and risk management and mitigating and managing failures at depth is useful, that education can come in many forms, although the "accepted" form is a prescribed course with a set content according to the experiences of a set group.

Regards

AnneMarie

[MaryS]

Don't be such a bloody tart

I'd be willing to risk buddying with you as a narcosis benchmark but I seem to give the impression of being narked on anything over 5m

Daz

P.S I reckon with your enquiring mind and background you will be pretty much ok on the self learning route.

Thanks Daz, of course I've just broken my all nails removing my provisional divers green "P" plate from the back of the casing which you kindly gave me. I'm not sure I want an IAM plate . You can always witness the narcosis level at my next dive at NDC on the 4th.

See you soon, Mary

[Drmike]

I look after the UK navy's rebreathers for a living.

Hey Mary, if you have any surplus Navy MK16 (MK27 UBA) bits and pieces you dont want I would be happy to help out

[turbanator]

I've just done Mod 1 on the Kiss and am OC qualified, so am in a similar position.

I have considered going the self-taught route, but ateotd, 'you don't know what you don't know'.
When we asked if there was any reason not to put a bit of helium in when diving to 40m or so, our instructor sait that it was up to us, after all there is no dive police, but did point out the insurance/dependants angle.

Since I've not quite finished the Mod 1 yet and have a healthy suspision of the thing, I think I'll run it with air dil for the best part of a year at least.

r
Paul

[Decodiver]

You know this discussion pops up periodically either here or on the list and it is enlightening to see peoples viewpoints.

I teach the Gas module at both diver and instructor level, I have yet to have a student with an OC mix ticket come on a CCR Gas Course who has said to me 'That's crap that is. I haven't learnt anything'. There are lots of competent people with OC mix tickets diving CCR without any problems.

Are they capable of working the unit as an O2 RB without the electronics?

Maybe, if someone has explained it to them.

Are they capable of running the unit manually?

Maybe, if they revisit their Mod 1 skills frequently enough.

Can they competently run the unit on SCR and calculate bailout scenarios and needs?

Maybe, if they are cerebral enough to think problems through before they happen, who knows?

I personally believe that whilst the gas logistics of mix CCR diving are relatively simple (when physically compared to OC), the limiting factor on OC, is how big a tank the diver can handle. In a way, that limits the amount of depth they can dive to, and with OC, people generally carry all their needed deco gases (I said generally!).

With CCR this is not the case. You could quite happily dive an alpine unit to 150m for 20 minutes without even bothering to calculate bailout needs or scenarios. That is why I personally tailor my gas courses to discuss, explore and use, bailout gases, in a controlled environment.

The skills are both fundamental and important, however, it is the knowledge gained from the gas discussions and scenarios, that benefit, in my opinion.

Cheers all

Dave Cooper

[BrianG]

Mary,
My son and I have just completed our Trimix ticket on the unit after a year of diving with air dil. During the year the deepest we have dived has been 45 metres, and for us the unit has been a revelation.
We found the theory side of the course was nothing like as gruelling as the theory on the initial course, but the exam at the end really was challenging. The practical side of the course was a different matter. It was very intensive and specific to the rebreather diver, an entirely different concept to open circuit Trimix diving. I do not wish to enter the debate regarding self improvement versus instruction, different strokes for different folks. I will just say that I learned a lot on the course, and it is reassuring to know that the person at your side is very competent when you simulate a complete electronics failure at 50 metres for the first time. Between us my son and I have almost 50 years of experience diving open circuit. Afterwards we both agreed the course was value for money and money well spent.
My thanks go to our instructor, Andy of Dales Diving, his excellent tuition has succeeded in raising our competence and confidence levels to a new height.

[Mark Chase]

I passed Mod 1 back in September and I put mix in the unit straight away. Initial dives were in the 35-40m range and I had no intention of being narked out of my skull stressed out on an unfamiliar bit of kit.

He was normoxic 21/35 and I deeply resent TDI/APD who ever putting me out side my terms of insurance for diving the safest diluent gas available.

To me depth was not an issue it was deco that was important. As a result I limited my diving to short deco / no deco dives where going straight to the surface was not going to kill me but might end up in the pot for a session.

On every dive I carried bail out gas and a deco plan so if it went wrong I would bail out to a familiar OC deco profile and ascend in comfort. This was all the security I needed to do the dive. If the unit so much as blinked an error I would bail out.

As it was I haven’t had to so far.

Personally I see all the potential bail out scenarios on a CCR as being straightforward in terms of deco and easily computed for in bail out plan. The need for a course to reiterate this to a qualified and experienced trimix diver is zero to me. However I hope the course will focus more on running the unit and staying on the loop in error modes so I have to rely less on OC bail out.

As far narcosis I can say it is similar to if not the same as OC. I dived the unit on air dill down to 64m in the red sea, assessed deco, took video, navigated a canyon and got out and drew a map of the dive site. All good fun in the warm low stress 20m viz environment of the red sea but I would not have liked anything to have gone wrong whilst I was down there.

Had I had the option of Trimix I would have grabbed it but the dive centre was only going to give me air as a dill as I was not Mod3 trained. Tats the main thing for me I have to have Mod 3 to get mix away from home so I have to have Mod3

IF the course has any thing earth shattering to offer I'll let you know as I do it in Feb

ATB

Mark Chase

[Decodiver]

Hi Mark,

However I hope the course will focus more on running the unit and staying on the loop in error modes so I have to rely less on OC bail out.

This is exactly the whole crux of the course. As you will know, having done your bail-out scenario calcs, it is impossible to carry enough OC bail out gas for really deep, long dives, on CCR.

If the course has any thing earth shattering to offer I'll let you know as I do it in Feb

You planning on getting another 86 hours in by Feb then?

Cheers

Dave Cooper