Heliox again !

[Iguana Don]

Dr. Powell,
I've been reading another forum, you probaly can guess which on, & the subject keep coming up. Is there any and how much study has there been on this topic. I still seems to me if N2 is such a problem, then get rid of it. Other than making you talk funny & the thermal charastics of He, what else, if any are the problems associated with diving on Heliox.
Could this be, as with any new "cutting edge" theory just be that there hasn't enough research? Or have I missed something?

 

[BillP]

Hi don:

I'm not Dr. Powell, and I'm no expert on heliox diving, but I'll take a shot at your question. Can I assume you're asking about heliox for recreational diving?

Helium has some benefits as a breathing gas for divers. Its primary benefit is probably the lack of narcosis. It also can have some benefits in decompression especially for saturation diving, but in the "recreational range" of dive times and depths nitrogen can be the better choice for many dives. The primary problems with using helium for recreational diving are cost and logistics. The U.S. Bureau of Mines set the price of Grade A helium at $37.50/1000 ft3 in 1986 (about 4¢ ft3). But when you add in the costs of handling, mixing, analyzing, etc., the cost to the diver is significantly higher. I believe that "techinical" divers estimate the cost of diving heliox at about $80-200 per hour for the helium. (At the depths that most "recreational" technical divers dive, nitrogen isn't needed but they often add it to their mix {trimix} reducing cost but adding another level of complexity.) Now add in the cost of having every recreational diving filling station set up to fill with helium (means having O2 too), analyzing every cylinder for O2 content, maintaining O2 cleaning for every cylinder that would be filled with the partial pressure blending method, etc., etc. and the cost skyrockets. Nitrogen is "free".

Now add in the logistical problems of training recreational divers about the decompression characteristics of helium and teaching them heliox tables. Many heliox tables call for a gas switch to nitrox or oxygen on ascent- will this also become the standard for your typical recreational diver? There could be a whole new market for heliox dive computers, at a premium price. Shall I go on?

The lack of narcosis makes helium a superb breathing gas for dives deeper than the recreational limits. Its decompression characteristics make it the gas of choice for saturation diving (adding nitrogen back in for deeper dives to reduce the High Pressure Nervous Syndrome from helium- but that's another story). But if you do a cost/benefit analysis for recreational diving, I doubt that many divers would find the marginal benefits of heliox in the recreational diving range worth the significant additional cost and compexity.

Just my 2¢,

Bill

(If anyone wants to correct my numbers, feel free.)

 

[Beck_narco_diver]

Ok here comes the info, well if you do not use nitrox i would first suggest that,
ok helium, helium is infact easier to breat as it is less dense then air. In rapid descents u can suffer from HPNS, It has high termal conductivity, your deco is longer, if you were not performing deco u will have to now, most people deco on air if they have been using heliox especially if it is a deep dive that you are doing, ie 66mtr + I personaly have trouble with narcosis so if you have tried nitrox consider normoxic trmix. By there is a lot of reseacrh in to Heliox, a lot of technical divers tend to eiter use that or trmix depending on their dive profiles, to be honest i would say that most people if they are going that technical they are using rebreathers, make life a little easier. But yeah loads of research. Try nitrox, normoxic trmix, trimix then heliox.

If you do not know not may people do not do heliox fill and yeah they can be pretty exspensive...

 

[Iguana Don]

Bill & Beck

Let's forget about the $.
I,ve been reading this subject on another forum.
Forgetting cost, dive computers, fill stations etc.
Wouldn't it be worth it if you could eliminate the N2 problem. I am exploring the possibilities of expanding my experience into overhead environment diving, I understand that this would blow the minds out of the cert. agencies if this was a suggested ave. for rec. diving.

Thanks for the reply

Don

 

[BillP]

Hi don:

I guess I don't really understand what you're asking. Exactly what "N2 problem" do you mean? If you mean narcosis, what kind of dive do you mean? A dive to 30 ft? Then no, diving helium would not be "worth it" for any reason that I can think of. Do you mean a dive to 300 ft? Then yes, by all means adding helium to the mix to reduce narcosis is "worth it". Do you mean a dive to 90-130 ft? Well, that depends on you. How "narced" do you get, what are you trying to accomplish at that depth, are you willing to put up with possible shortened no decompression limits or longer decompression times on helium, etc? Some might say that it's "worth it" to dive heliox at 130 ft or shallower, but I bet most would not. Most would probably say that it's "worth it" to add helium below 130 ft, but others would not. What's "worth it" to you?

The way you're asking the question is like asking, "Is it worth it to have a sledgehammer?" Well, what are you trying to accomplish? Are you repairing Swiss watches? Then no, having a sledgehammer in your toolbox isn't worth it. Like a sledgehammer, helium as a breathing gas is a tool. It might be right for some jobs but not others. For some jobs, nitrogen might be a better tool, for others, hydrogen might have benefits. You might even find a job where neon makes the best inert gas in the mix. Learn the characteristics of the different breathing gas mixes and pick the one that's best for the job. No one gas mix is best for every dive. If you're planning to dive deep enough where narcosis will be a factor, long enough where mandatory decompression time becomes an issue, and skilled enough where you can handle gas mix changes at depth, then I'd say yes, learning about when diving with helium in your gas mix would help is "worth it".

HTH,

Bill

 

[Beck_narco_diver]

Bill i have been trying to fond what tables abysimal seem to havew for their new computer the abyss explorer i think it is, do u have any information on it, or at least and details on any published papers

 

[BillP]

Hi Beck_narco_diver:

I only know what I read on their website. For what it's worth, they say that the Explorer computers use a "Modified Abyss" algorithm ( http://www.abysmal.com/pages/features-explorer-deco.html ). I would assume that this is a proprietary algorithm of Abysmal Diving, Inc. Elsewhere on the website in a review article ( http://www.abysmal.com/pages/features-explorer-deeptech.html ) they say that the Abyss algorithm "uses a decompression algorithm based on a 32-tissue Buhlmann model with a RGBM (Reduced Bubble Gradient Model) Bubble Mechanics model superimposed."

HTH,

Bill

BTW, your post was titled "Neox and argox" but your question was about Abysmal's computers. Best I can tell, the Abysmal computers only handle O2/N2/He mixes and don't give info on neon or argon mixes. (It'd be pretty unlikely that anyone would be using argon as a breathing mix anyway since it is denser, more narcotic, less favorable for decompression, and more expensive than nitrogen. I can't think of a good reason to use it.)

 

[Beck_narco_diver]

Ok i heard a rumor that the abysmall computer allowed for neox, weel aside from that do u know of any other documentation or testing completed usinf this gas

beck

 

[BillP]

Hi beck:

Studies were done on neon as a breathing gas in the 50's, 60's, and 70's. Neon would be an OK breathing gas for diving. Neon is not thought to cause narcosis (or at least causes significantly less narcosis than nitrogen.) Its fat solubility is similar to helium's so it should share some decompression characteristics similar to helium. Its densisty (0.8 g/L- at 1ATA) is similar to nitrogen's (1.1 g/L) but five times that of helium (0.16 g/L) so it would not distort divers' voices significantly, but it would have the same density limitations as nitrogen on very deep dives (where the gas gets too dense to breathe easily). The primary problem with using neon as a breathing gas is cost. As I mentioned above, the US Bureau of Mines set the base wholesale cost of helium at about 4¢ per ft3; neon costs closer to $50-60 per ft3.

With its lack of narcosis, neon would be beneficial on deeper dives where nitrogen narcosis would be a problem. Its lesser effect on voice distortion (than helium) is also a plus. But its depth limitations due to density and its extremely high cost seriously limit its usefulness as a breathing gas. Helium doesn't have the depth limits of neon, it is also non-narcotic, and the voice distortion it causes doesn't offset its cost benefits compared to neon. I can't imagine you'd ever see neon used as a commercial diver's breathing gas and almost certainly never as a recreational diver's breathing gas. I would doubt that you could easily find decompression tables for neox diving. Recreational dive computer manufacturers won't be adding neox to their decompression algorithms anytime soon.

HTH,

Bill



[Edited by BillP on 11-13-2000 at 05:56 AM]

 

[Dr Deco]

Helium was first proposed for use as a divers breathing gas by Elihu Thomson in a series of letters to W.R. Watson of the General Electric Laboratories in the 1920s. The reason for this was to avoid the limitation on depth that was set by the then-supposed limitation on the availability of oxygen at depth. The idea was based on “the principle of superior rapidity of diffusion of the low density gas” [Thompson, E, 1927. Helium in deep diving. Science, 65,36 – 38.]

In addition, the physical chemist J. H. Hildebrand suggested to Sayers and Yant of the Bureau of Mines that the lower solubility of helium compared to nitrogen would be of value in preventing caisson disease. They tested this in experiments with guinea pigs. The gas was tested in human experiments by Edger End in 1937 [Rapid decompression following inhalation of helium-oxygen mixtures under pressure. Amer. J. Physiol, 120, 712 – 718.] to make its lower solubility when compared to nitrogen. Theoretically, if a gas did not dissolve at all in a liquid, there would not be any gas at all to form bubbles. In actuality, the difference in solubility between helium and nitrogen is primarily only in lipid (fatty) tissues.

Further, the substitution of helium for nitrogen came when divers began descending below 200 feet and nitrogen narcosis entered as a serious hazard. This narcosis, sometimes referred to as the rapture of the deep, was a result of the narcotic effects of nitrogen when under pressure. This narcosis is not evident when helium is used as the diluent (for oxygen) in deep diving.

Since recreational divers typically do not descend below 130 feet, the narcotic effect may be evident but is not particularly bothersome. Technical divers go deeper and therefore helium would be of value. Furthermore, tech divers switch from heliox to nitrox mixtures below about 200 feet to speed decompression because nitrogen is taken in slower than helium is eliminated.

If there is not an advantage for heliox at depth shallower than 200 feet, and additional problem with helium is its cost in comparison to compressed air. Frankly, there are not any advantages for a recreational scuba diver (<130 fsw) with a helium/oxygen mix compared to a nitrogen/oxygen mix.

{PS I was away at the NAUI meeting and am behind on these posts.}