Heliox ?

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

Iguana Don

Guest
Messages
2,203
Reaction score
4

Can you fill your tank with O2 & He instead of O2 & "air", wouldn't this eliminate all the nitrogen problems. Please give me an answer other than tech divers use tri-mix.

I've read all about that, but they still use O2, "air" & He.
Only problem I can see is the cost factor & availability.

Don


 
Trimix is used mainly for cost considerations. Helium is real expensive stuff.

The other reason is a pure O2-He mix will cause High Pressure Nervous Syndrome when diving deep. The pure oxygen starts to cause you Central Nervous System (CNS)to mis-fire. By adding a bit on Nitrogen to the mix, this problem is averted.

A better breathing gas for sport divers is Nitrox. This gas is simply enriched air, with a higher mix of oxygen. Air is comprised of about 21% O2 and 79% N2. A typical nitrox blend will run from 30% to 36% O2 and the remainder is N2. The downside to diving Nitrox is you have to give up depth. The higher percentage of O2 will cause CNS Oxygen Toxicity seizures if you exceed the Maximum Operating Depth for your specific mix. It sounds a little scary, but with good training (its a fun class) and proper dive planning its safer than diving air.

Nitrox, when you just too old for air.
 
:bounce: Finally, thanks for the answer Sharkbait, I've taken the Nitrox class from Pay Now Dive Now Org, but still couldn't get an answer to my question, had to come to the real world to get an answer. Thanks again & may all your dives end on the surface.


Don
 
I found the Pay And Dive Immediatly instructors I knew taught Nitrox, but had no idea how the stuff worked. They could read tables all day long, but if you asked them a question that wasn't in the book they were stumped.

I ended up taking my Nitrox cert from a TDI technical instructor, she made sure we knew the gas inside out and backwards.

 
Hi Don,
Air is fine for most sportdiving depths. EANX is even better, but not for deep diving as is a common misconception as you well know. (Nitrox is a swell decompression gas/travel mix.) Trimix is super for deep diving, as you don't get gooned on the high nitrogen percentage. There are special proceedures though on the decompression from trimix as helium tends to come out of solution VERY fast, and therefore ascent rates are super-critical. Also, trimix tends to make one very cold during a dive and extra thermal protection is needed, such as a drysuit. This also provides extra buoyancy if needed, due to the weight of additional tanks needed to contain the vast amount of gas one breathes at depth. Heliox is better for the deeper stuff as no nitrogen is needed but deco is still sticky and cold is still a problem. As depth progresses, some nitrogen must be added back to the mix and no one yet knows why. (We are talking VERY DEEP.) Just a quick, thumbnail view of some of the many gases divers use. Norm
 
Hello,

For a very VERY indept text on this topic look at the iantd technical diving encylopedia. They quote the NEDU reference about adding trace amounts of nitrogen to heliox to overcome some critical issues while at depth (extreme depth I think) They have a list of pro's and con's about nitrox and suggest we decompress on heliox with high o2 levels in place of nitrox. Also states that several deco chambers are now treating DCI patients using heliox/o2 inplace of air/nitrox/o2. Overall it's a much much safer gas but there's 3 big disavantages, cost, availability and production.

Ed
 
Actually heliox is not really that great for deep diving due to HPNS?Sorry,all the studies show that the min depth for HPNS is around 500' or so.Also descent rate played a great part in that to.Heliox isn't used primarily because of cost,but it is much easier to get bent on He than Nitrogen.Why? you ask.He is uptaken and off-gassed much faster.The pressure gradient with He is greater at the same given ascent rate due to it's decreased density.Download any of the free software at Jim Cobb's site to see if there is any deco advantage to Heliox.Also,don the fire-retardent suit and go to the techdiver list and bring this up.I wouldn't trust what I say or anyone else here who isn't a Mix instructor.Do the research from here,but if you're going to try this type of diving get certified instruction.This stuff ain't rocket science,but they don't call it "technical " for no reason.Try Blacknets referenced reading while you're at it.
 
Hello,


That's why they add a trace amount of nitrogen, for the HPNS, and the depth is shallower than 500' btw.

Yes there is a slight increase in deco time with helium than nitrogen but medicaly helium is much safer to dive with than nitrogen. Besides those figures you was running was based on deco of standard gas, not 'hot' mixes and switching to 100% o2 ASAP.

I would not be caught dead on the techdiver list as there is nothing they can't back anything they say up with facts, and when someone does bring up facts they get flamed and other similar issues (not to mention they disown the dead to help statistics in their favor).

So from this I get my information from places like iantd, usn and noaa. If you really want the lowdown on this subject then the man to talk to is rainreg. He's the expert in the field and wrote the standards for many things, not to mention his HUGE array of credentials.

Ed
 
Like many of the folks have already said, the #1 factor is $$.
Heliox is good to past 1200', where the mixture starts to get too thick to breath easily. There have been dives to the 2000' mark using hydreliox (hydrogen & oxygen) but you'd never catch me inhaling a potentially explosive mixture, even if the O2 content is very low.
There is a slightly increased deco obligation with heliox because it saturates the deep tissues more quickly, even though it offgasses faster. (ref: USN tables)
Don't know beans about trimix, my exposure to mixed gas has been in a commercial environment rather than recreational.
 
Hi guys-
First, it is difficult to apply some of these references I have seen offered in regard to helium use. Commercial diving depths and exposures are not applicable to "recreational" type dives.

HPNS is not a major issue for technical dives. Forget about that...

Some misconceptions:
Helium is not bad in regard to decompression. In reality, you will incur a *less* severe decompression penalty from helium than nitrogen. I know what the references say and what the deco programs spit out. They are wrong. Helium is very friendly. Most deco programs will penalize you for higher helium (versus nitrogen) content in your mix which is converse what should happen.

Helium does not necessarily play a big role in "cooling" you down, with the exception as a insulating gas. Yes, you do feel cooler at depth, but I think this is largely due to the fact that you are not impaired by narcosis. I remember diving wet, on air, off VA and MD to 180' and not having any issues with temperature. However, diving to 180' on mix, wet, off FL, in temperatures 30 degrees greater than VA, I can stil catch a chill.

Heliox is not used due to cost and logistics of pumping. Primarily, the second issue. You need a booster pump to get the needed pressures of a heliox mix and not every person or shop has access to a booster.

FWIW, we have been using heliox 50/50 (along with 100% O2) for decompression with great results. Totally eliminating nitrogen during deco is the way to go.

Cheers,
Mike
Association of Underwater Explorers
http://www.mikey.net/aue
 
https://www.shearwater.com/products/teric/
http://cavediveflorida.com/Rum_House.htm

Back
Top Bottom