Helium Fraction and Standardized Gases

[boulderjohn]

I was just curious about how GUE arrived at their gas mix philosophy.

I understand that if it is not broken, dont fix it. But how did these mixes become sacred to begin with ?

What was the basis for the decisions that these are the right mixes and not some other combination?

I took my Ratio Deco class from Andrew Georgitsis, who used to be with GUE. According to what I recall from what he said about that history (and his review of it was more of an off hand remark in reply to a question, not a formal part of a presentation), it was somewhat random. It had to do with what could be easily made given banked gases. (Please note the qualifiers in that explanation.)

What I am going to say next is also based on that class. I say it with some hesitation because I mentioned the key idea of it in another thread a while ago, and someone who should know told me I was wrong, and then someone else who should know said that I was right. There was no follow up.

I recently had a very informative email exchange with JJ about Ratio Deco. According to what I understood in that exchange, Ratio Deco originated by a process that was designed to recreate the ascent profile that deco software would create within certain specific parameters, and those parameters would include using those gases.

He did not say this in that exchange because we were actually on a slightly different topic, but my conclusion was that if you want to use Ratio Deco, you have to use those gases. With UTD, it is very clear. UTD's deco theory is very much based on Ratio Deco, for they do not use anything else for dive planning. The idea of standard gases is very firmly in place there for that reason.

 

[TSandM]

If you look at the desired END and ppO2, standard gases keep both within desired limits for the depth range, and all but 30/30 can be mixed by adding helium and topping with 32%, which is generally banked. Hard to argue with that . . .

 

[Bombay High]

Thank you John and TSM .

 

[rlynch]

Good question Bombay and answer ts&m & john

 

[PfcAJ]

I took my Ratio Deco class from Andrew Georgitsis, who used to be with GUE. According to what I recall from what he said about that history (and his review of it was more of an off hand remark in reply to a question, not a formal part of a presentation), it was somewhat random. It had to do with what could be easily made given banked gases. (Please note the qualifiers in that explanation.)

What I am going to say next is also based on that class. I say it with some hesitation because I mentioned the key idea of it in another thread a while ago, and someone who should know told me I was wrong, and then someone else who should know said that I was right. There was no follow up.

I recently had a very informative email exchange with JJ about Ratio Deco. According to what I understood in that exchange, Ratio Deco originated by a process that was designed to recreate the ascent profile that deco software would create within certain specific parameters, and those parameters would include using those gases.

He did not say this in that exchange because we were actually on a slightly different topic, but my conclusion was that if you want to use Ratio Deco, you have to use those gases. With UTD, it is very clear. UTD's deco theory is very much based on Ratio Deco, for they do not use anything else for dive planning. The idea of standard gases is very firmly in place there for that reason.

You can create a ratio for just about any gases at any depth. The standard gases work well with easy to see and use ratios, but the same 'idea' can be applied to other gases at other depths, or even 'standard' gases at oddball depths. Obviously, teaching a million different ratios would be silly, but you can derive your own for specialty dives.

 

[Kevrumbo]

Someone please help me to understand. I have to admit I stopped reading Kevin's posts a while back because they all seemed to ask the same question and make the same point over and over again. I think the point was answered over and over again. Someone please tell me where I am misunderstanding.

Kevin's point seems that there are better mixes that can be used for deco than the standard mixes used in DIR diving. That concept is frequently called "best mix" by other agencies.

In conceding that point, DIR says that those advantages may be real, but they are not as significant as some people seem think. This is indicated by the fact that a system for using standard gases during ascent has been worked out and it is working just fine.

There are advantages to using standard mixes apart from this issue.

In the DIR judgment, the advantages of using standard mixes outweigh the advantages of using a best mix philosophy.​

Please tell me where I am misunderstanding.

I was always taught standardized gases were "minimum helium content" and that 21/45 or 21/55 could be still be considered a standardized mix.

Major point being that this differs from the 'best mix' practice of computing O2 content exactly based on some target max PPO2 and potentially having everyone showing up with different "best mixes" for the same dive (resulting in different decompression strategies, team separation on deco, etc).

Kevin uses 'best mix' in a really nonsensical way where the WKPP using 21/45 or higher helium mix would be considered "best mix" and a nonstandard gas, and that leads to a contradiction with JJ running a training agency promoting standardized gases based on the experience in the WKPP while simultaneously diving "best mix" blends in the WKPP. Pretty sure that if kevin tried to go over to the GUE forums and claim that in the grenade-hurling way that he has here that he'd get corrected as to what those terms mean and how they're used...

Well, taking your question at face value....

It predates the GUE forums by about 8 years.

Also, it is occasionally useful to pick up newer rec divers that are curious and don't know where to go for more information.

But the number of actual instructors and WKPP members on here is pretty limited, and Todd Kincaid appears to be quietly reading this thread and munching on his popcorn.

The kinds of questions that Kev is asking are well outside of the scope of diving that most members of this forum are doing, and Kev refuses to listen to Nick and most everyone else has given up. So if Kev wants a better authority -- JJ and Casey are both on the GUE forums -- and would probably be happy to put that 1999 article into context, and to set the record straight on what "best mix" and "standardized gases" mean along with what WKPP uses for 21% deco gas and how long a dive needs to be to require upping the helium content. And they'll have actually been informed by first-hand discussions with a lot of the decompression researchers.

The fact that Kev sits in the DIR forum on SB and lobs cut+pasted grenades at people and is afraid of the actual GUE forums should tell you all you need to know about him, however...

I'm sure the cost-factor makes it prohibitive.

Because its prohibitively expensive, there's also just not as much of a track record.

Do you know anyone that uses 21/79 on a routine basis? Maybe some CCR divers with more money than sense...

And JJ has a very strong bias to not fix something that isn't broken...

You need to show actual problems on actual dives that it solves (not solving theoretical problems on dives on paper), which is a principle that underlies most GUE/WKPP procedures. If you look at George's old "what is a stroke?" rant there's a line there which addresses this: " If you see something that [...] is designed to accommodate some phobia while ignoring all else, you are dealing with a stroke." That's the problem with solving theoretical issues at the exclusion to all else which is that eventually you'll run across the law of unintended consequences and you'll start causing more problems than you solve.

A silly example would be a diver worried about a collapse who drags a ton of shovels with him who is found dead tied up in line around all that gear.

Being paranoid about IBCD to the point of only using helium might work out okay, or you might find out that while some helium is good that completely eliminating nitrogen becomes counter-productive in some way... To avoid solving only theoretical issues, though, and to avoid reconfiguring your breathing gas simply because you're phobic of IBCD, you need to actually have encountered issues or know of dives that have encountered issues with 21/35 or whatever...

So with all that said above . . .what was the definitive point supposedly answered again and again by DIR Practitioners that justifies adding more Nitrogen to a deco "standardized mix" than that of the bottom mix, despite all basic fundamental principles of Gas Physics and Decompression Physiology and intuitive common sense logic?

The Original Post #1:
http://www.scubaboard.com/forums/dir/396160-helium-fraction-standardized-gases.html#post6043491

 

[Crush]

If I am the OP, can I ban someone?

 

[Kevrumbo]

"Because it works"; "Everybody does it and nobody seems to be getting bent"; "IBCD not a real world issue, only theoretical hoohah".

All meaningless rationalizations above indicative of a Group Think Fallacy within the SB "DIR Practitioners":

Groupthink is a psychological phenomenon that occurs within groups of people. It is the mode of thinking that happens when the desire for harmony in a decision-making group overrides a realistic appraisal of alternatives. Group members try to minimize conflict and reach a consensus decision without critical evaluation of alternative ideas or viewpoints. . . The more amiability and esprit de corps there is among the members of a policy-making ingroup, the greater the danger that independent critical thinking will be replaced by groupthink, which is likely to result in irrational and dehumanizing actions against outgroups. . . Groupthink - Wikipedia, the free encyclopedia

One of the dangers of our world today is group-think. It occurs as a person lets identification with a group cloud their reasoning and deliberations when reaching a position on a given issue. At best, it is a rhetorical device. At it's worst, it can be a very harmful replacement for sensible thought. In fact, it is considered one of the common fallacies of modern society. . . Understanding the evils and dangers of group-think - by Dr. G. A. Anderson - Helium

The Original Post #1:
Helium Fraction and Standardized Gases

 

[PfcAJ]

Well then, the question and thesis still remain: If no one is getting bent and IBCD seem to be a non-issue for all but the most extreme bottom times, why add more helium to the gas? Its a simple logical means to an END.

See original replies from...everyone.

 

[ucfdiver]

"Because it works"; "Everybody does it and nobody seems to be getting bent";

All meaningless rationalizations

Call it group think if you want, but using historical evidence beats using your own body as a test subject, at least in my opinion. I'm sure racking up all those frequent flier miles on medevac in route to the chamber has it's benefits (free class upgrade and first name service?), but it's not something I'm interested in. I'll stick with the data I have, group think or not.