recreational trimix

[WreckWriter]

Just for the record I can tell you that GUE cards ARE widely accepted in Florida.

Tom

 

[joens]

MechDiver once bubbled...


Is there an agency that gives trimix cert without dives??? Or do you mean EAN?

Phil [/QUOTE

well when the " rec" agencies get into trimix as they did with nitrox it is inevitable someone will come up with a course with no required dives . After all the reasons they give for not requireing dives for nitrox will be the same reasons they will give justifying not needing it for trimix .
joens

 

[MechDiver]

WreckWriter once bubbled...
Just for the record I can tell you that GUE cards ARE widely accepted in Florida.

Tom

As I would expect them to be Tom. I was thinking more about West Bumscrew, Montana

I'm sure it won't be a problem, just based on how limited trimix availability is lots of places, it would be a question I'd ask if taking the class.

Phil

 

[Genesis]

that will hold.

The big deal with 'mix, even at "recreational depths", is ascent control. Blow it with Nitrox and it might not be a big deal. Blow it with mix, from what I understand, and you may be getting a nice chamber ride, even if you otherwise did everything "by the book."

While I don't believe that EANx "training" consists of anything more than academics, the reality of mix is that if you don't have good buoyancy control and control of your ascent rates you're likely to bend yourself. That alone ought to mandate that actual dives be conducted, and it also ought to mandate that without that control you shouldn't be able to pass the class.

In fact, I'd go so far as to suggest that if you take the class that at least one dive should have to be made on Nitrox, with an instructor, to verify that you HAVE the ascent rate control necessary to safely use the 'Mix - BEFORE you dive it.

 

[WreckWriter]

MechDiver once bubbled...
As I would expect them to be Tom. I was thinking more about West Bumscrew, Montana

I'm sure it won't be a problem, just based on how limited trimix availability is lots of places, it would be a question I'd ask if taking the class.

Phil

You're right, the LDS in West Bumscrew only accepts PDIC cards

Tom

 

[WreckWriter]

Genesis once bubbled...
The big deal with 'mix, even at "recreational depths", is ascent control. Blow it with Nitrox and it might not be a big deal. Blow it with mix, from what I understand, and you may be getting a nice chamber ride, even if you otherwise did everything "by the book."

Karl,

Where are getting this information/theory? Sounds like a recreational agency scare tactic to me.

There's a danger of DCS from fast ascents on any gas, to my knowledge its no greater on helium mixes than on any other gas.

Tom

 

[MechDiver]

joens once bubbled...
well when the " rec" agencies get into joens

Ah, but they already have. The GUE course is recreational triox

As I have not been folded, spindled or multilated by a nitrox diver who did not do any cert dives, I don't let it worry me much.

Phil

 

[MechDiver]

WreckWriter once bubbled...


Karl,

Where are getting this information/theory? Sounds like a recreational agency scare tactic to me.

There's a danger of DCS from fast ascents on any gas, to my knowledge its no greater on helium mixes than on any other gas.

Tom

I would assume because He offgasses much faster than nitrogen? That was stressed in my class, slow "controlled" ascents were a "must do". True, more important for deeper stops I believe, but I think Genesis is correct.

Phil

 

[Genesis]

Where are getting this information/theory? Sounds like a recreational agency scare tactic to me.

Its a matter of perfusion....

He perfuses faster than N2 does, both in and out. This makes ascent rate control (and deep stops for those doing deco) more important than it is on Nitrogen-based gasses, because the critical tension differential before you get bubbles is likely smaller for He than it is for N2.

My understanding (and this is from doing a LOT of reading on the subject; I haven't managed to "bend" myself yet and hopefully won't!) is that He-based gasses require much more studious attention to ascent rates and deep stops than N2-based gas does.

Looking at deco schedules for both Mix and Air at depths in the 180-190' range, and also in the 100-130' range, it appears that for most recreational (e.g. "NDL" style) exposures there is no SIGNIFICANT difference - that is, you could even dive Trimix using a Nitrox computer, provided that the mix was either normoxic or hyperoxic (so the O2 percentage can be set), IF you keep ascent rates under 30ft/min.

For deeper exposures there are some exposures where the deco curve "inverts" (that is, it takes MORE time to deco on 'Mix than Air), so for planned-deco diving, particularly "spikes", you have to be even more careful, and the idea of using a non-He-based model looks VERY dangerous in those situations.

But for the "normoxic" or "hyperoxic" Trimix diver within recreational depth limits, the primary concern beyond the usual MOD and NDL concerns appears to be one of ascent rates, and from the playing around with deco planners that I have access to it appears (and I stress - this is from my playing around with dive planning software on the surface - I don't have hard facts to back this up) that you could dive Normoxic Trimix on an air table within the NDLs and be ok.

 

[MASS-Diver]

Interesting.

I'm planning in the future to learn to dive with He-mixes for what some people consider close to rec depths (there are several wrecks I want to dive in the 130-160' range) which is alot different from wrecks in the 300-400' range. When I began to discuss this with peope their response, these were people who knew alot about diving (DMs, instrucuctors, etc) but where not TRIMIX cert, was that I would be racking up alot more deco time at these "shallow depths" with MIX as opposed to air.

But, as I just ran through V-planner - deco time for a 130' for 30minutes with air was just about identical to that of triox (21). Now if only He itself was so darn expensive.