Why do you need to decompress from Heliox?

[JonnyB]

Can someone please explain how it come that you need to do deco after a certain time, when using Heliox.
I mean if you remove all the Nitrogen from the mix, which is the gas that you need to decompress, what is it left?
Does Helium have similarities to Nitrogen but in a more forgiving maner, due to the fact that it is more dence?
I am not talking about 3mix, oxygen, nitrogen and helium mixes, i am talking about Heliox(Oxygen, Helium).

And can anyone tell me at what depths you use neon as a mix.

Regards
Jonny

 

[Snowbear]

Can someone please explain how it come that you need to do deco after a certain time, when using Heliox.
I mean if you remove all the Nitrogen from the mix, which is the gas that you need to decompress, what is it left?
Does Helium have similarities to Nitrogen but in a more forgiving maner, due to the fact that it is more dence?
I am not talking about 3mix, oxygen, nitrogen and helium mixes, i am talking about Heliox(Oxygen, Helium).

And can anyone tell me at what depths you use neon as a mix.

Regards
Jonny

Here's a thread currently running on this very topic.

A simplified answer - As you probably know, Nitrogen is an inert gas (not metabolized by the body) that is absorbed by the tissues under pressure. It needs to be allowed to off-gas at an appropriate rate for the depth and time spent there to prevent injury, right? Even "NDL" dives need to be dealt with this way via slow ascent rates, "safety" stops and surface intervals.

Well, Helium is also an inert gas. It's molecular weight is lighter than Nitrogen, so it on- and off- gasses about twice as fast. So - yes, a decompression schedule must still be followed when breathing helium. It's not used in breathing mixes to eliminate decompression obligations, but to reduce the narcosis caused by nitrogen.

I read an article a while back about someone trying Methane - found it - Go here, click on Free Articles - the article on Methox is about 1/2 way down the page.

 

[ArcticDiver]

Snowbear's answer was great. But there is a more basic and even simpler answer. Your body needs two gasses for life. Oxygen to support life and carbon dioxide to trigger your breathing response. Lots more technical than that but this level does for what we are talking about.

For the rest of the gases we are only concerned about the "soda pop effect" and the toxic/depressing effect of gasses under pressure. So, we offgas slow to minimize or even avoid forming any bubbles in the body. We mix up different formulas of breathing gas to minimize any nasties to the body.

How much of what to use under what circumstance and how long to spend at what pressure to minimze or avoid bubbles is something filled with opinions. I haven't seen any of the latest tables generated from Navy research which might shed a lot of light on the subject. But pre-Navy research folks, incliding some pretty high speed science types, have ideas and some pretty good logic to support those ideas, but very little actual human biological testing.

Since it is your life you can see why questions about specific gasses and depths are best answered for yourself after you personally do the in-depth research. You have to make critical decisions that don'treally have cut and dried answers beyond the gas's basic chemical properties.

 

[Snowbear]

Is this ArcticDiver from Fairbanks? Welcome to ScubaBoard

 

[roakey]

And to anticipate the follow-up question...

The reason you substitute one [somewhat] inert gas that you have to outgas for another inert gas that you ALSO have to outgas is because He is less narcotic at depth.

There is also mounting evidence that in gassing and out gassing He is much easier on the body than N.

Roak

 

[detroit diver]

...........

And can anyone tell me at what depths you use neon as a mix.

Regards
Jonny

You use it at depths when your light won't work. A couple of strategically placed electrical attachments to your body, and you can then glow bright pink or green depending on the mix..!!

 

[chrpai]

http://www.techdiver.ws/exotic_gases.shtml#3.2

 

[Diver0001]

Can someone please explain how it come that you need to do deco after a certain time, when using Heliox.
I mean if you remove all the Nitrogen from the mix, which is the gas that you need to decompress, what is it left?
Does Helium have similarities to Nitrogen but in a more forgiving maner, due to the fact that it is more dence?
I am not talking about 3mix, oxygen, nitrogen and helium mixes, i am talking about Heliox(Oxygen, Helium).

And can anyone tell me at what depths you use neon as a mix.

Regards
Jonny

About the Neon thing. As far as I know you could theoretically use Neon as a diving gas in the same way (and for the same reasons) you use helium. However, aside from some experiments I haven't heard of any wide-spread use of Neon. Probably boils down to a cost thing and the fact that helium tables are available and helium probably gives you shorter deco schedules etc etc.

R..

 

[ArcticDiver]

"Is this ArcticDiver from Fairbanks? Welcome to ScubaBoard "

Thanks, the Board finally let me back on.

I'm looking forward to a lot of fun on this Board.

When I couldn't get back here I sent you an email. As soon as I get my regs back from their annuals I plan on coming down to the Banana Belt and diving in either Whittier or Seward.

 

[BigJetDriver]

As was stated in the other thread:

Heliox

--------------------------------------------------------------------------------

Folks,

It all boils down to this (if Doc Deco will pardon the pun).

(1) Argon insulates better than air or a mixture with helium in it. It is an excellent choice for drysuit inflation gas.

(2) Argon is much more soluable in lipids (your body fat), as the good Doc pointed out. It therefore would provide no advantage in a decompression schedule.

(3) Worse than that, however, is the fact that argon is much more narcotic than nitrogen. Since nitrogen is much more narcotic than helium, argon can be ruled out as a breathing gas at depth.

(4) Heliox is a much better choice for deep diving, especially on a rebreather, when combined with decompression programs that deal effectively with the helium, such as Wienke's RGBM.

(5) Given the cost of helium, a tri-mix suitable for the chosen depth makes better economic sense for an OC recreational technical diver.

(6) At extreme depths (i.e. >600+ fsw), a mix that is mostly heliox with a "pinch" of nitrogen in it (sounds like a recipe from Emeril) has been found to leaven the effects of HPNS. Of all tech divers world-wide, 99.5% will never operate in that depth regime.

Hope that helps!

BJD

ALSO:

Jonny,

Certain agencies and groups, such as COMEX in France, and NEDU in the United States, have experimented with neon as part of breathing mixtures. Its largest drawback, however, is its relative status as "un-obtanium"! Neon constitutes an extremely small fraction of the atmosphere, and producing it in quantities suitable for diving operations makes the price of helium seem extremely cheap by comparison.

Neon is slightly more narcotic in its effect than helium, so, given its extra effort and expense, it is just not worth bothering with.

Relative Narcotic Potency: Helium 0.23, Neon 0.28, relative to Nitrogen 1.00

(Page 190, Table 15-2, of Diving and Subaquatic Medicine, by Edmonds, Lowry, Pennefather, and Walker, Fourth Edition, Arnold Publishing 2002, available in the U.S. from Best Publishing)

BJD