standard mixes

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Permalink Reply by Maciej Arkuszewski on May 21, 2009 at 12:51pm

Hey Alexis.

In UTD we strongly believe that, due to gas density any mix, without He in it, is increasing likelihood of CO2 build up at depths bigger than 30m. CO2 is highly narcotic and it is also proven to precipitate CNS tox much sooner and at much lower PPO2s, than what is commonly used as a safe margin. From UTD standpoint one of standard mixes for 30-40m range is 25/25. RD, gas management and NDL tables for that gas are extensively explained in Rec3 course. I strongly recommend that you consider taking Rec 3 or similar course before making a plunge below 30m.

So in essence: There's no RD for non-standard mixes which also violate max END of 30m rule.

Regards
Maciek

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Permalink Reply by kevrumbo on June 8, 2009 at 11:39pm

On the wrecks of Chuuk Lagoon, the Truk Odyssey Liveaboard offers free-of-charge Nitrox30: I used the Minimum Deco subset of Ratio Deco with a 10% EAD for a range of depths from 21 to 33m. The other deeper wreck dives I did were with Air Mix on the Hoki Maru at 43m; Nippo Maru 47m; and the San Francisco Maru at 51m, and have successfully used RD 1:1 with Ean50 and O2 for deco. And yes, RD 1:1 can be used with Air Bottom Mix if you must use it --but of course beware of the extreme narcosis that may be encountered. . .

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Permalink Reply by Jeff Seckendorf on June 9, 2009 at 7:17am

Kevin,

Ratio Deco is designed for standard gases. Anything outside of the standards, you're a test pilot. We don't advocate, condone, teach, recommend, or use non-standard gases. As Maciej said, the addition of helium to the breathing mixture reduces the potential for CO2 buildup, and it reduces the narcotic properties of the high-nitrogen mixes. We keep the equivalent narcotic depth above 100'/30m, so that's our max depth for air and Nitrox 32. Period.

A "successful" dive to 51m on air with two deco bottles is so far outside our standards that the only real way to address it is to re-read (and re-read, and re-read) the above paragraph.

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Permalink Reply by Maciej Arkuszewski on June 9, 2009 at 8:01am

Kevin.

What you fail to mention is that, by your own account, you also got bent doing those dives with that strategy. That's not the safety margin we are comfortable with.

Regards
Maciek

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Permalink Reply by kevrumbo on June 9, 2009 at 3:48pm

Incorrect attribution your part Mac . . . I was not bent as you claim as an end result of this strategy. (Air Mix versus Trimix Ratio Deco, was not the issue here):
Type I Bends Hit in Chuuk
Regards to You & Jeff As Well,
Kev
Maciej Arkuszewski said:

Kevin.

What you fail to mention is that, by your own account, you also got bent doing those dives with that strategy. That's not the safety margin we are comfortable with.

Regards
Maciek

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Permalink Reply by kevrumbo on June 9, 2009 at 3:54pm

Agreed Jeff . . .for all the caveats that you and Maciej as UTD Instructors have noted.

As a layperson/testpilot/guinea pig by your characterizations --nevertheless I can only relay and attest to the anecdotal instances that I've experienced. Respect on your part for the veracity of my experience, despite the non-standard protocol, would be very much appreciated. . .

Jeff Seckendorf said:

Kevin,

Ratio Deco is designed for standard gases. Anything outside of the standards, you're a test pilot. We don't advocate, condone, teach, recommend, or use non-standard gases. As Maciej said, the addition of helium to the breathing mixture reduces the potential for CO2 buildup, and it reduces the narcotic properties of the high-nitrogen mixes. We keep the equivalent narcotic depth above 100'/30m, so that's our max depth for air and Nitrox 32. Period.

A "successful" dive to 51m on air with two deco bottles is so far outside our standards that the only real way to address it is to re-read (and re-read, and re-read) the above paragraph.

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Permalink Reply by Jeff Seckendorf on June 9, 2009 at 4:06pm

So with all due respect, Ratio Deco is not an anecdotal protocol.

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Permalink Reply by kevrumbo on June 9, 2009 at 4:16pm

Jeff Seckendorf said:

So with all due respect, Ratio Deco is not an anecdotal protocol.

Well technically from a scientific method point-of-view, Ratio Deco in general is all anecdotal evidence (i.e. in comparision to a model like RGBM undergoing trials with the US Navy Experimental Dive Unit etc.).

But I get the gist of your meaning.

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Permalink Reply by Maciej Arkuszewski on June 9, 2009 at 5:10pm

Kevin.

You are more than free to promote your own ideas on your own web site. We repeatedly stated that deep air diving is not advocated in any form by UTD and we will not allow for advice we deem unsafe to be dispensed from our site. That includes advocating RD to be used on gases other than our standard set. If you wish to continue to debate that you should find another forum.

Maciek

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Permalink Reply by kevrumbo on June 11, 2009 at 5:28pm

Maciej Arkuszewski said:

Kevin.

You are more than free to promote your own ideas on your own web site. We repeatedly stated that deep air diving is not advocated in any form by UTD and we will not allow for advice we deem unsafe to be dispensed from our site. That includes advocating RD to be used on gases other than our standard set. If you wish to continue to debate that you should find another forum.

Maciek

Again, I wholeheartedly agree with you Maciek (and Jeff) for the prudent reasons you both have articulated. If you feel that you have to place a disclaimer on instances of deep air diving for liability and safety issues, then do so and state it for those reasons . . .but not in the guise of censorship.

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Permalink Reply by Mark Chase on December 5, 2009 at 11:58pm

Maciej Arkuszewski said:

Kevin.

You are more than free to promote your own ideas on your own web site. We repeatedly stated that deep air diving is not advocated in any form by UTD and we will not allow for advice we deem unsafe to be dispensed from our site. That includes advocating RD to be used on gases other than our standard set. If you wish to continue to debate that you should find another forum.

Maciek

The above sums it up nicely. I spent years arguing that GUE were wrong in many ways before the fog of anger relating to the insulting behavior on the net of some of its disciples lifted and I could see it for what it really is.

Standardized diving is a compromise in many ways but it offers a wealth of advantages over non standardized diving.

So go with the flow or get out of the river.


Obviously you can use ratio deco for any sort of diving using any set of gases. You just can’t use the UTD diving system unless you stick to the rules.

Personally I have done many dives below 30 on air. Hundreds probably. Deepest air dive was 70m done probably 10+ over 60m. Sure you can dive air and use RD there’s hardly any difference between a 45m air profile and a 45m 21/35 profile but its not UTD so take it somewhere else because I have seen enough people narked silly at 45m to know its not that sensible.

I haven’t been below 30m on air for about four years now and if I can avoid it I won’t be doing it any time in the future.



ATB

Mark Chase

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Permalink Reply by kevrumbo on December 6, 2009 at 7:26pm

Again, environment has a lot to do in how you cognitively and comfortably tolerate narcosis. I'm down here in warm 29deg C tropical waters of Truk Lagoon, no current, good visibility --at 52m on the San Francisco Maru-- and I'm feeling pretty good enjoying the scenery on deep air and decoing out using Ratio Deco . But going out of the light zone into a cargo hold or an overhead engine room line penetration at that depth raises the anxiety level, because I know I don't have full mental faculties to deal with adversity, especially cascading or "domino" failures & contingencies. l'd be reluctant to try this depth in the cold dark & rough waters back home in SoCal on deep air. . .

Comparing air with 20/20 mix, even this light trimix surprisingly made a big difference in terms of narcosis abatement and ease of breathing at 52m on the Aikoku Maru (and much less fatigue post-dive) . . .and at only $160 for a twin 11L set on open circuit, a more economical solution rather than spending over $300 for standard 18/45 mix (Helium here in Truk Lagoon is $0.14/L or $4/cu ft). And Ratio Deco works with this mix as well. . .

Use what gases you've got along with Ratio Deco, and be prepared to mitigate the risks during the dive if you don't have the necessary standard bottom mixes. . .

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