TDI and hyperoxic trimix

[Thalassamania]

Really, so explain the following excerpt: ...

Your quote was taken from a review article in the August 1965 issue of Naval Research Reviews published by the Office of Naval Research. We've learned a bit in the last thirty-three years. While helium is a wicked conductor of heat it's thermal mass is rather low. Living in a heliox environment can be a chilling experience, but heat carried off the body by thermal transfer through the lungs to the breathing mix is a whole 'nother story, I've been told that it's actually less than air.

I believe that the reason for gas warmers on surface supplied rigs are more to help keep the diver comfortable, warm breathing media is real sweet, we even played with a 2% hydrogen mix and a platinum catalyst in the line for scuba ... 130 degree moist air coming out the regulator. There's no better place to provide warmth than at the body core, air, nitrox, tri-mix, heliox, it doesn't matter, warm is nice.

 

[Steve SDI/TDI HQ]

Yes... we call it a trimix class. :blinking:

TDI was one of the instigators of making recreational trimix training readily available to interested divers (technical diving is recreational diving remember). The first-level course is designed to teach divers how to use ANY and all trimix and heliox blends that are "safe" to breathe at 1-bar (≥18 percent oxygen) to a maximum depth of 60 metres. There is no minimum depth set for graduates; however, at least two dives must be conducted deeper than 40 metres. As a Trimix instructor, I have always considered this "two dives deeper than..." aspect of standards as part of a requirement for gas (volume) management rather than having anything to do with narcosis... which in my opinion comes a distant third or forth in the hierarchy of associated risks to diving below 40 metres.

 

[Divin'Papaw]

Yes... we call it a trimix class. :blinking:

TDI was one of the instigators of making recreational trimix training readily available to interested divers (technical diving is recreational diving remember). The first-level course is designed to teach divers how to use ANY and all trimix and heliox blends that are "safe" to breathe at 1-bar (<18 percent oxygen) to a maximum depth of 60 metres. There is no minimum depth set for graduates; however, at least two dives must be conducted deeper than 40 metres. As a Trimix instructor, I have always considered this "two dives deeper than..." aspect of standards as part of a requirement for gas (volume) management rather than having anything to do with narcosis... which in my opinion comes a distant third or forth in the hierarchy of associated risks to diving below 40 metres.

There, you have your answer. I'm just getting started on my training with TDI but I assumed this was the answer. Nice to hear it directly from TDI.

Not sure why these discussions have to always take on an attitude. If you wanna dive trimix at 50' and you can afford it, have a blast. Kinda like the folks driving Hummers. Hey, if you can afford the gas, enjoy. If another diver doesn't need it until 140', good for them. Every tech diver needs to know their limits and dive within them.

The problem starts when the view is expressed, often times unsaid but implied, that EVERYONE should be on trimix if they're diving deeper than 100' (or 90' or 85' ... pick your limit) or they're being reckless. IMO that's just not a fair characterization and is painting with a awfully broad brush.

 

[Steve SDI/TDI HQ]

Presume that is a typo for >18 percent oxygen. ?

Whoops... not enough caffeine this morning... thanks... and more correctly &#8805; (greater than or equal to)

 

[texdiveguy]

Dang I am glad we cleared all this up....was thinking I needed to search out another agency to get one of those 30/30 cards....just in case I wanted to dive that mix......

 

[battles2a5]

What makes you think GUE trained divers are unable to calculate a 'best mix'?
This feels like a 'I'll make my own 'best mix' and I dont care what everybody else uses' versus a team approach. I can calculate TDI's 'best mix' for any ppO2/ppN2 thank you but I choose to dive standardized mixes because I, personally, just believe that the standardized mix approach is preferable over everybody dives their own mix approach.
I also doubt that TDI's 'best mixes' have great advantages over GUE's standard mixes. But I'll run some profiles in V planner and see what the results are. I prefer/use 30/30 for anything in the 80 - 100'ish range.

I don't think anyone is accusing you of not being able to calculate a best mix. You are also wrongly assuming that calculating "best mix" precludes the use of team diving procedures. As a team, you can determine the dive plan, determine the desired mix, the deco gas, the schedule. Everything can still be done as a team (but it doesn't have to, to each his/her own).

I'm not arguing that standard mixes are not a good thing. As a new-ish technical diver myself, I am trying to keep to standard gases as I experiment with deco schedules. I want to try to limit the number or variables in my dive plans so I can learn how my body reacts to specific changes. I will likely stick to standard gases (not necesarrily GUE-standard) as I gain experence but would I would not disqualify myself from a dive if standard mixes were not available. I would rather rely on my own thinking for my gas planning as opposed to what someone else has told me is the "right" gas for MY dive.

 

[BarryNL]

The problem starts when the view is expressed, often times unsaid but implied, that EVERYONE should be on trimix if they're diving deeper than 100' (or 90' or 85' ... pick your limit) or they're being reckless. IMO that's just not a fair characterization and is painting with a awfully broad brush.

No, I think it depends on the person and the dive - certainly within the 100' or so range. I wouldn't bother with trimix for Caribbean reef dives in the 100' range, but for North Sea wrecks where you have currents, visibility below 6', holes dynamited into wrecks which make unintentional penetration dives possible, fish nets and line strewn everywhere, etc. I don't see trimix as an extravagance.

 

[BarryNL]

I'm not arguing that standard mixes are not a good thing. As a new-ish technical diver myself, I am trying to keep to standard gases as I experiment with deco schedules. I want to try to limit the number or variables in my dive plans so I can learn how my body reacts to specific changes. I will likely stick to standard gases (not necesarrily GUE-standard) as I gain experence but would I would not disqualify myself from a dive if standard mixes were not available. I would rather rely on my own thinking for my gas planning as opposed to what someone else has told me is the "right" gas for MY dive.

Fair enough, but there is more to GUE's standard gasses than simply getting the whole team on the same stuff. GUE also teaches their "battlefield planning" techniques which basically allow you to do everything from EAD, CNS% and OTU tracking to entire deco schedules quickly in your head - but these calculations only work with the standard gasses. Very little in the GUE philosophy is one-dimensional

 

[muddiver]

Your quote was taken from a review article in the August 1965 issue of Naval Research Reviews published by the Office of Naval Research. We've learned a bit in the last thirty-three years. While helium is a wicked conductor of heat it's thermal mass is rather low. Living in a heliox environment can be a chilling experience, but heat carried off the body by thermal transfer through the lungs to the breathing mix is a whole 'nother story, I've been told that it's actually less than air.

I believe that the reason for gas warmers on surface supplied rigs are to help keep the diver warm. Warm breathing media is real nice, we even played with a 2% hydrogen mix and a platinum catalyst in the line for scuba ... 130 degree moist air coming out the regulator.

Oh, thanks for the update. I went through basic mixed gas in 1995 and the instructors were all old oil patch divers who should have retired ten yreas eairlier. The quote was my attempt to find the information I "knew" existed, but is not in the new U.S.N. manual. I think it might be in the Commercial Diver Training Manual the Best Publishing use to print.

 

[battles2a5]

Fair enough, but there is more to GUE's standard gasses than simply getting the whole team on the same stuff. GUE also teaches their "battlefield planning" techniques which basically allow you to do everything from EAD, CNS% and OTU tracking to entire deco schedules quickly in your head - but these calculations only work with the standard gasses. Very little in the GUE philosophy is one-dimensional

We are on the same page. I'm not saying there is anything wrong w/ standard gases, or GUE gas planning. I think it is a very good way of doing it and a good system in general. But it isn't the only way of doing and I don't think it is fair to assume that if you are not practicing GUE standard gases that you are a cowboy. That's all I was trying to say.