Heliox...

[J1M1]

I've heard that Heliox is sometimes used for really deep dives to decrease nitrogen consumption. Since there is no nitrogen in the mix (Heliox not Heli-air) does that completely eliminate the risk of getting bent? Or does helium pose a similar risk?

If it does eliminate the risk, why doesn't everyone dive Heliox instead of EANx? Is it a cost thing?

Just curious,

- PolsVoice.

Helium will change the deco schedule alot, caling for deeper stops to offgas the helium although it does offgas quicker than nitrogen, it also ongases quicker, especialy at depth. If you could find a gas that could be used with O2 to mix that would completely negate the possibility of getting bent you would change the diving industry forever. Heliox would have to be used over trimix on especially deep dives where all deco performed would be to ofgas the helium. But then again other factors come to concer such as HPNS.

 

[BigJetDriver]

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 a recreational technical diver.

(6) At extreme depths, 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 :anakinpod

 

[J1M1]

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 a recreational technical diver.

(6) At extreme depths, 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 :anakinpod

excellent points

 

[JonnyB]

what about neon? at what depths do you use Neon as a breathing gas?

/Jonny

 

[BigJetDriver]

what about neon? at what depths do you use Neon as a breathing gas?

/Jonny

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 :anakinpod

 

[Kendall Raine]

Below about 600 fsw, the risk of HPNS makes heliox a POOR choice for breathing gas. Heliox is used in commercial application as an intermediate depth gas. Nitrogen is added to heliox to form trimix for deep dives >~600 fsw as small amounts of nitrogen tend to ameliorate HPNS. Hence, in commercial settings, trimix is for especially deep dives, not heliox. The primary reason trimix is used by sport divers in intermediate ranges is cost. As sport diving has evolved, helium's numerous advantages have been recognized by sport divers and it is being used increasingly at shallower depths (100-200) instead of air or nitrox.

Helium will change the deco schedule alot, caling for deeper stops to offgas the helium although it does offgas quicker than nitrogen, it also ongases quicker, especialy at depth. If you could find a gas that could be used with O2 to mix that would completely negate the possibility of getting bent you would change the diving industry forever. Heliox would have to be used over trimix on especially deep dives where all deco performed would be to ofgas the helium. But then again other factors come to concer such as HPNS.

 

[J1M1]

Below about 600 fsw, the risk of HPNS makes heliox a POOR choice for breathing gas. Heliox is used in commercial application as an intermediate depth gas. Nitrogen is added to heliox to form trimix for deep dives >~600 fsw as small amounts of nitrogen tend to ameliorate HPNS. Hence, in commercial settings, trimix is for especially deep dives, not heliox. The primary reason trimix is used by sport divers in intermediate ranges is cost. As sport diving has evolved, helium's numerous advantages have been recognized by sport divers and it is being used increasingly at shallower depths (100-200) instead of air or nitrox.

but the amount of nitrogen in the mix is meager. The amount is dependant on what the indutries assume is enough to offset the symptoms of HPNS. I was just answering the original post without going into detail. I think that the studies of how much nitrogen should be present to offset tremors in divers was done by COMEX. Heated hydrogen is also being used to replace nitrogen in the mix hte combination being called hydreliox. Both are to offset tremors and allow divers to work clearheaded at depth. Clearheaded meaning able to function somewhat productively in simple tasks. Yes, the nitrogen has always been for cost. I dive poor mans mix as well. usually 18/40. J.D.

 

[DepartureDiver]

what about neon? at what depths do you use Neon as a breathing gas?

/Jonny

Last I looked, neon was about $800 for about a 200 cubic foot bottle.