I was wondering

[wolfpack]

I am not trimixed certified, but at 100 feet does 30/30 give you more bottom time than ean 32? if I am 30 then can I stay longer at 100 feet vs nitrox 32? thanks!

[Doppler]

wolfpack once bubbled...
I am not trimixed certified, but at 100 feet does 30/30 gove your more bottom time than ean 32? it I am 30 he can I stay longer at 100 feet vs nitrox 32? thanks!

The short answer is no. One dives with helium mixes not to prolong one's bottom time (as is usually the case with EANx mixes), but to manage the risks of oxygen toxicity and inert gas narcosis. When one dives with trimix, one is not trying to stay within the NDL of recreational (sport) diver tables.

Hope this helps

DD

[omar]

The use of 30/30 is now being advocated for “recreational” dive profiles by GUE (it is only a matter of time before the other agencies jump on the bandwagon). There really is no such thing as a NDL dive. While a guy called MHK (a GUE instructor) is claiming that you will have longer bottom times using 30/30 vs 32% I do not believe that assertion.

I base this on the fact that helium on gasses and off gasses at a greater rate than nitrogen. A common value you see quoted is 2.65 based on the solubility differences of He vs N2. I have not seen any studies that have determined that this is the actual rate. There are a couple that indicate the off gassing rate of He is 2-2.5 times greater than N2.

This is an important facet of diving with He because ascending from a dive at a fast a rate means inadequate decompression. A proper rate (~30 fpm) will minimizes bubble growth and expansion and controls desaturation better when compared to faster rates.

However, there are numerous other benefits to using 30/30 vs 32%, such as reduced breathing effort and an associated reduction in CO2 production & retention, a lower narcotic level, and in my opinion you just feel better. The latter may just be a result of doing a proper ascent. As an aside my wife and I currently dive 30/30 the same as 32% (single tank) and have not had any problems.

omar

[WYDT]

omar once bubbled...
However, there are numerous other benefits to using 30/30 vs 32%, such as reduced breathing effort and an associated reduction in CO2 production & retention, a lower narcotic level, and in my opinion you just feel better. The latter may just be a result of doing a proper ascent. As an aside my wife and I currently dive 30/30 the same as 32% (single tank) and have not had any problems.

Omar, I can definitely vouch for the benefits of "shallow" Helium. I've used 30/30 on several of my recent cave dives where the depths ranged from as little as 40ft to around 100max. I've previously done these dives on 32% (EAN) and can tell you there is a marked difference when doing the same dives on 30/30.

I feel more alert and see things I didn't see before. I never felt "narked" before on the 32% but definitely see a difference with 30/30... Helium GOOD!

[MikeFerrara]

I love helium but I can't see divers who cry over a $5 tank of air ever paying for trimix for the same dive.

Even mixing it yourself it gets expensive not to mention time consuming.

[WYDT]

MikeFerrara once bubbled...
I love helium but I can't see divers who cry over a $5 tank of air ever paying for trimix for the same dive.

Even mixing it yourself it gets expensive not to mention time consuming.

true.... I'm hoping as it becomes more widely accepted that the price will drop some.

[Capt Jim Wyatt]

Helium is pretty expensive here in the Lower Keys. For me to fill a set of doubles (200 FT3) costs me about $30 in helium alone.

As far as decompression obligation goes, my calculations indicate a 60 minute dive to 100fsw on 30/30 requires 43 minutes of decompression. While the same depth/Bottom time on EAN32 requires only 31 minutes of decompression. Both instances the back gas is used for deco.


The additional cost coupled with the additional deco time does not seem to warrant the use of Helium at 100fsw.

The benefit is certainly virtually no narcosis. A 30/30 mix at 100 fsw has an Equivalent Narcotic Depth of 34 feet. So your mental state is the same as diving air at one atmosphere.

[wolfpack]

What software are you using for your calculations showing the 100 foot dive on ean vs he? Just curious.

Thanks everyone for the response, the reason I ask is that I saw where MHK was stating on another news group that 30/30 would increase bottom time. It was my opinion that it did not, although I am barely versed on this subject. As I read further everyone else disagrees with mhk and says that it does not add bottom time. MHK is a gue instructor so I am not really sure where he is coming from.???

[nradov]

wolfpack once bubbled...
at 100 feet does 30/30 give you more bottom time than ean 32?
The question as stated makes no sense, or seems to be based on a flawed assumption. You can stay on the bottom as long as you want with either gas. Then you'll have to do the correct deco. For a short bottom time it would be about the same deco with either gas. 100ft is a little deep for nitrox anyway.

[SimonN]

Capt Jim Wyatt once bubbled...
Helium is pretty expensive here in the Lower Keys. For me to fill a set of doubles (200 FT3) costs me about $30 in helium alone.


$30, is that all?

To get twin faber 12Ls (100cuft fabers) filled with 45% He costs AU$175 (~US$100), just for the helium.

It would be AU$117 (~US$70) for 30%.

Could explain the lack of DIR divers (who actually do any real diving) and the fact the most of the tech divers (actually doing the dives) are using CCRs here in Oz.

Wolf pack - there is anecdotal evidence that helium is less damaging to the bodies tissues than nitrogen and offgasses 'better'. This could have been translated as more bottom time for the same amount of deco?

Personally, there is no way you'd get me diving on 30/30 unless someone else was paying, I know I am no where near narced enough at 30M (100ft) on air/nitrox to miss anything worth not missing.

[Doppler]

wolfpack once bubbled...
What software are you using for your calculations showing the 100 foot dive on ean vs he? Just curious.

Thanks everyone for the response, the reason I ask is that I saw where MHK was stating on another news group that 30/30 would increase bottom time. It was my opinion that it did not, although I am barely versed on this subject. As I read further everyone else disagrees with mhk and says that it does not add bottom time. MHK is a gue instructor so I am not really sure where he is coming from.???

One of the challenges with this type of forum is that you can never be sure that your question is worded so that everyone understands it the way you intended and likewise with replies...

The original question was: Does it extend bottom time, and at the time I assumed the framework for that was: Does it allow me to extend my bottom time without getting into a staged decompression obligation. The answer to that -- regardless of whether a neo-Haldanian or non-Haldanian algorithm is used -- is no. Putting all the benefits of adding helium aside... because that is beyond the parameters of the question... there is another side to the coin.

The practice of adding 30% helium for a "recreational" dive -- which is one with no staged deco, one assumes -- is certainly up for debate entirely because of the transit times of He and the common practice of executing deep and short stops on ascent with trimix -- even trimix with 30% O2.

Since the average recreational diver has been clocked at ascent rates in the 120 fpm range -- and that is an average! -- trimix and recreational or dives within NDL -- seem to be mutually exclusive unless we radically change what passes for an advanced openwater program. Something I would support but which I believe at least one of the major certifying agencies will resist because it will mean failing some people.

Take care

DD

[DIR Tec Diver]

Go to www.wkpp.org and read George's informaiton on Deco. You will also notice that they never go above 1.2ppo2. Never bump up the O2, always opt for added helium. If you use some decompression programs and say you are utilizing helium, you get penalized, they are not designed that way. Don't input that nor plan it that way, it is not accurate. The Buhlmann model specifically will screw you big time. Buy the GUE decoplanner, read the manual, read George's information, and you will be on track to doing things the right way.

No one knows deco better than George, and he and his group have perfected it. Also go for standard mixes. Forget mixing all the things for specific dives, it is a waste of time, money, effort and can complicate things. Those mixes are on the site as well

[wb416]

Doppler once bubbled...

[snip]

Since the average recreational diver has been clocked at ascent rates in the 120 fpm range -- and that is an average! -- trimix and recreational or dives within NDL -- seem to be mutually exclusive unless we radically change what passes for an advanced openwater program. Something I would support but which I believe at least one of the major certifying agencies will resist because it will mean failing some people.

Take care

DD

That's probably why GUE Fundamentals is the prerequisite for GUE recreational Triox. It helps weed out the 120 fpm nonsense.

[disclaimer: Taking Fundies isn't enough... obviously one must exhibit good skills]

[Doppler]

wb416 once bubbled...


That's probably why GUE Fundamentals is the prerequisite for GUE recreational Triox. It helps weed out the 120 fpm nonsense.

[disclaimer: Taking Fundies isn't enough... obviously one must exhibit good skills]

Hey: no argument here... :) The issue isn't with GUE... but one of those mainstream agencies with the big market share... stop smiling Bob!


Take care

[wb416]

Doppler once bubbled...


Hey: no argument here... :) The issue isn't with GUE... but one of those mainstream agencies with the big market share... stop smiling Bob!


Take care

:) :D :)

Whooooo? Meeeee? ;)

[Doppler]

DIR Tec Diver once bubbled...
Go to www.wkpp.org and read George's informaiton on Deco. You will also notice that they never go above 1.2ppo2. Never bump up the O2, always opt for added helium. If you use some decompression programs and say you are utilizing helium, you get penalized, they are not designed that way. Don't input that nor plan it that way, it is not accurate. The Buhlmann model specifically will screw you big time. Buy the GUE decoplanner, read the manual, read George's information, and you will be on track to doing things the right way.

What on earth does any of this have to do with the original question or anything else that's being discussed here? And exactly which algorithm does your version of Decoplanner use?

[/B]
No one knows deco better than George, and he and his group have perfected it. Also go for standard mixes. Forget mixing all the things for specific dives, it is a waste of time, money, effort and can complicate things. Those mixes are on the site as well [/B]

George is a terrific project manager and his team has done some kick-ass stuff, but I'd argue that Dr. Bruce Wienke knows a little bit about decompression: and who said anything about NOT using standard mixes?

Who are you? Isn't being a P.A.D.I. instructor and DIR sort of mutually exclusive?

Whoops... that just slipped out.

DD

[wb416]

Doppler once bubbled...


What on earth does any of this have to do with the original question or anything else that's being discussed here? And exactly which algorithm does your version of Decoplanner use?



George is a terrific project manager and his team has done some kick-ass stuff, but I'd argue that Dr. Bruce Wienke knows a little bit about decompression: and who said anything about NOT using standard mixes?

Who are you? Isn't being a P.A.D.I. instructor and DIR sort of mutually exclusive?

Whoops... that just slipped out.

DD [/B]

Come on Steve... surely you've been around long enough to recognize a sockpuppet masquerading as a troll!

Look through his history... he came on like gang busters on Day 1 and everytime he comes on board he leaves a swath of pillage and plunder wider than "Sherman's March"...



[Editor's Note: Not to be patronizing, but I realize you're not from the States, so just in case, the "march" reference is to a U.S. Union General's march through the south in the U.S. Civil War.]

[Doppler]

wb416 once bubbled...


Come on Steve... surely you've been around long enough to recognize a sockpuppet masquerading as a troll!

Look through his history... he came on like gang busters on Day 1 and everytime he comes on board he leaves a swath of pillage and plunder wider than "Sherman's March"...



[Editor's Note: Not to be patronizing, but I realize you're not from the States, so just in case, the "march" reference is to a U.S. Union General's march through the south in the U.S. Civil War.]

Oh... have I been hooked... drat!

Bob, the Sherman references are understood, but you better watch out using that kinda language when you're down in cave country... some of those nice southern folk might mistake you for a yankee! Hang on a minute... more than half of the folks down there are yankees. YIKES!

Take care mate

Doppler:D