Rec Trimix

[Diesel298]

The usual thread you expect on this topic with the normal mix of dogma, dis-information, personal/agency agendas, tech wannabees, conspiracy theories, etc.

Personally, I would never place myself in a situation of having any deco obligation without being equipped with redundant doubles and a 1/3 reserve as an absolute minimum and preferrably also an accellerated deco gas. A single and a pony for deco? - not in this lifetime with or without helium.

To avoid the semantics that have popped up regarding the stops/slow ascents required with rec trimix as opposed to just calling them "deco stops". I'll define "deco" as meaning any dive where I could not do an ESA from what ever depth I am at directly to the surface. If a direct ascent is not possible, - it's an overhead dive and I will equip accordingly.

I do dive deep air to 150 ft and do it in dark, cold, freshwater environments. I accept the arguments that narcosis can impair both your problem solving skills and memory ability, but I also have to say that the degree of impairment is manageable in many circumstances and does not have to contra-indicate the dive. These dive regularly include exploratory mapping dives where we do in fact remember what we saw to an acceptable degree.

It's also an individual thing based on experience, mental capacity, training and pre-planning of the dive. I'll draw an analogy to flying an instrument landing approach on a partial panel to minimums in heavy turbulence and gusty crosswinds. Some people have the ability to do it with adequate precision while others just don't and never will. So in short, your mileage will vary.

In my opinion He has some serious limitations. It draws more heat from you through respiration which is a big issue on open circuit scuba in cold water. It also requires a separate inflation gas (air, or argon if you are overly technically inclined and like to add expense for no real gain) to reduce heat loss in your dry suit. In my experience this make He much less desireable in cold water.

Helium is a much "faster" gas in terms of ongassing so you acquire a deco obligation faster at depth (particularly shallow depths) compared to air or nitrox and as inidcated above it is more demanding in terms of ascent rates as it also off gasses faster.

It is also very expensive compared to air or Nitrox. If you have unlimited funds and it does not reduce the number of dives you do, it's perhaps not a problem. However I have met trimix divers who tend to dive trimix in any situation where they can justify it with the result that they dive a lot less due to funding limitations than they would if they spent the same available funds diving air.

And realistically, there is a trade off some where between the greater mental clarity conferred by trimix versus the value of perhaps 3-4 times the recent and lifetime experience diving air. I'd rather do several dives a week on air than maybe 1 or 2 every other week or so on trimix.

Overall, I really have a hard time seeing how the pros of trimix could outweigh the cons at depths shallower than 100-130 ft. I think in the real world it probably serves as an introductory course to develop a potential market of divers who may decide later to go on to normoxic or hypoxic trimix courses that then serve a real purpose allowing deep dives at depths below 150 ft.

good post.

 

[TheRedHead]

Lamont handled that earlier.

No CESA != No Deco. Helium on-gasses much faster.

 

[lamont]

Personally, I would never place myself in a situation of having any deco obligation without being equipped with redundant doubles and a 1/3 reserve as an absolute minimum and preferrably also an accellerated deco gas. A single and a pony for deco? - not in this lifetime with or without helium.

which nobody in this thread has actually suggested. impressive destruction of a red herring though.

In my opinion He has some serious limitations. It draws more heat from you through respiration which is a big issue on open circuit scuba in cold water.

no it doesn't. helium has a higher heat conductance, but much lower heat capacity than O2 and N2 because its a monatomic gas. i don't notice any worse cold on 30/30 vs. 32% dives on OC.

It also requires a separate inflation gas (air, or argon if you are overly technically inclined and like to add expense for no real gain) to reduce heat loss in your dry suit. In my experience this make He much less desireable in cold water.

you're free to think i'm deliusional, but i believe i can tell the difference between argon and air.

if you check out my "look at me I'm DIR" profile pic, that's an LP14 argon bottle strapped to a single 130 with EAN32 for backgas.

Helium is a much "faster" gas in terms of ongassing so you acquire a deco obligation faster at depth (particularly shallow depths) compared to air or nitrox and as inidcated above it is more demanding in terms of ascent rates as it also off gasses faster.

yes. not a big deal.

It is also very expensive compared to air or Nitrox. If you have unlimited funds and it does not reduce the number of dives you do, it's perhaps not a problem. However I have met trimix divers who tend to dive trimix in any situation where they can justify it with the result that they dive a lot less due to funding limitations than they would if they spent the same available funds diving air.

i've got a set of doubles with 30/30 and a set of doubles with EAN32. i fill them up when they get low. i dive whenever i want to with the correct gas that i want.

And realistically, there is a trade off some where between the greater mental clarity conferred by trimix versus the value of perhaps 3-4 times the recent and lifetime experience diving air. I'd rather do several dives a week on air than maybe 1 or 2 every other week or so on trimix.

i dive several times a week on nitrox, and once or twice every other week or so on trimix.

Overall, I really have a hard time seeing how the pros of trimix could outweigh the cons at depths shallower than 100-130 ft. I think in the real world it probably serves as an introductory course to develop a potential market of divers who may decide later to go on to normoxic or hypoxic trimix courses that then serve a real purpose allowing deep dives at depths below 150 ft.

i really don't understand why there's all these people on here who are so threatened by recreational use of trimix. whats the big deal to you how i dive? is trimix such a badge for you that you can't possibly share it with someone who only goes down to 100 fsw?

i don't know... i'm done... you can believe about my diving whatever you want...

 

[TheRedHead]

I don't feel threatened by it. I'm just trying to understand it and compare constrasting information from various sources.

 

[JeffG]

You forgot it is possible to do that dive on Nitrox with no deco.

Every dive is a deco dive.

 

[lamont]

i dive in new england so no sympathy here man
its cold, and dark.. and on the wrecks theres nets and entanglements....
being narced at 100 fsw means ya need to dive more...
but hay for the guy who dives a dozen deep dives a year and wants to stroke it out and feel good about themselves..
have at it
its your day

all you want to do is slam, so i'm done.

i really can't understand why my diving to only 100 fsw on 30/30 annoys you so much...

 

[lamont]

I don't feel threatened by it. I'm just trying to understand it and compare constrasting information from various sources.

that wasn't directed at you.

 

[JeffG]

No CESA != No Deco. Helium on-gasses much faster.

CESA is a bad solution to a bad problem.

 

[TheRedHead]

Every dive is a deco dive.

That's what TDI says. But some decos are longer than others.

 

[TheRedHead]

CESA is a bad solution to a bad problem.

I'm not the one who brought up CESA. You're picking on me, Jeff.