Normoxic trimix

[InkDiver]

I'll bite. What would be a scenario where you'd need to identify your deco tanks in a zero viz situation? Wouldn't you be doing your deco in the open water while ascending?

I think you are assuming that deco is always done on 100% O2 and always at 20ft in OW. There is plenty of deco done deeper inside caves, etc, where this is important.

 

[Rhone Man]

When I started getting into tec I wanted to make the leap to trimix early, but I was persuaded to wait a while. Introducing helium into the mix throws in new wrinkles. Some of the gurus on the board can pick me up where I slip, but from recollection the key "new" things were:
- He is absorbed and off-gases much faster; conceptually you approach deco in a new way because He is much less forgiving.
- Risk of HPNS
- The nitrogen "step" - not jumping to a deco gas which has a significantly higher partial pressure of nitrogen (can't recall the reason for this, but I remember that it was a bad idea)

However, my understanding is also a lot of what you say is true - you also build further on skills you already have. It is just that before where you might have used one or two stage bottles, now you have three or four (and they are bigger). And if something goes wrong, you are (literally) deeper in the *$&%#.

I am hoping to do a trimix class next year. Until then I will just enjoy the narcosis buzz and/or fret about the fact that my fins are eating my legs.

 

[boulderjohn]

When I started getting into tec I wanted to make the leap to trimix early, but I was persuaded to wait a while.

It's a debatable point. Some agencies hold off on introducing He until you have really done a lot of tech work first. Others start you off with He relatively early in the process.

 

[JeffG]

It's a debatable point. Some agencies hold off on introducing He until you have really done a lot of tech work first. Others start you off with He relatively early in the process.

old thinking vs new thinking.

Rhone Man description is very 90's.

 

[Rhone Man]

It's a debatable point. Some agencies hold off on introducing He until you have really done a lot of tech work first. Others start you off with He relatively early in the process.

You are correct of course, and I should have mentioned that. I think some agencies even introduce helium for some non-decompression diving.

 

[Rainer]

For normoxic trimix, which the OP is asking about:

- He is absorbed and off-gases much faster; conceptually you approach deco in a new way because He is much less forgiving.

Nonsense.

- Risk of HPNS

Nonsense

- The nitrogen "step" - not jumping to a deco gas which has a significantly higher partial pressure of nitrogen (can't recall the reason for this, but I remember that it was a bad idea)

Nonsense.

If the above is what you learned in your class and why you didn't want He included for your 150' dives, ask for your money back.

 

[battles2a5]

When I started getting into tec I wanted to make the leap to trimix early, but I was persuaded to wait a while. Introducing helium into the mix throws in new wrinkles. Some of the gurus on the board can pick me up where I slip, but from recollection the key "new" things were:
- He is absorbed and off-gases much faster; conceptually you approach deco in a new way because He is much less forgiving.
- Risk of HPNS
- The nitrogen "step" - not jumping to a deco gas which has a significantly higher partial pressure of nitrogen (can't recall the reason for this, but I remember that it was a bad idea)

However, my understanding is also a lot of what you say is true - you also build further on skills you already have. It is just that before where you might have used one or two stage bottles, now you have three or four (and they are bigger). And if something goes wrong, you are (literally) deeper in the *$&%#.

I am hoping to do a trimix class next year. Until then I will just enjoy the narcosis buzz and/or fret about the fact that my fins are eating my legs.

The absorbtion and release of He is no reason not to dive it. HPNS and IBCD are not really practical issues in the limits of the normoxic class. You also are not likely to be carrying 3 to 4 bottles at this level, either, at least not in OW. These things come into play during the advanced mix class. I really see no reason not to hit normoxic sooner rather than later, and I would definitely not take Extended Range on air in lieu of a normoxic trimix class. Rhone Man- your situation ( and location for that matter) is a little different given the lack of availability of He, but if you can get your hands on it you are better off diving it.

 

[Tomeck]

I am already advanced trimix diver. Trimix diving is not cheap.

 

[battles2a5]

I am already advanced trimix diver. Trimix diving is not cheap.

Buy a rebreather. Then the "trimix" part gets cheap, but the "diving" part gets more expensive

 

[Packhorse]

Being pedantic (you know me well enough to know that I am!), that's not what you want to learn..... that's what you want to acheive. Your probably in a position to just buy some helium, blend your own mixes, cut your tables from Vplanner and do the dive.

The question is why don't you do that? What is it that you think you are lacking in order to do this safely? That's what you want/need to learn.

I guess its a question of not knowing what I dont know.
For $4k I would hope to learn a lot but as it is I simply cant figure out what that would be.

Can you do a valve drill 1' above the muck and not silt it up? Can you do a valve drill with no mask? Can you identify your deco tanks in a zero Vis situation? Can you hold a stop at 20' on O2 mid water with no reference and handle your O2 reg free flowing? Can you do all these thing while being tack loaded with other problems? Can you pick up and drop bottles on the go without affecting your buoyancy? These are just a few of the things we did in class some already could some needed practice. Have you thought about what to do when one of your deco regs does not work? The list is long and the instructor will make a big difference. My Normoxic instructor was so so, but full mix instructor was awesome. 4k is pricey you could fly to the US take the class and still save money.

Correct me if I am wrong but they are not necessary things involved in normoxic trimix. If I cant do those things now it will be practice that will make those things easy. Not spending $4k on a weekend course. ( im not saying I cant do these things but Im also not saying I couldnt improve on them either).
As it is I believe my skills are good enough for the types of dives I do now. Im not looking at adding another 2 mixes to the dive or going to much greater depths. I am simply talking about changing the gas mix I use for dives I am currently doing.