Heliox!

[padiscubapro]

Yes, and I was working on a Commerical job in a Hard Hat back in December last year and we were doing 210' mixed gas on Heliox. Thats why I was asking. because it elliminates any nitrogen if I am correct.

The detailed answer is much too complicated to get into online and unfortunately many instructors don't really understand the pluses and minuses of both..

The biggest difference is in dive time.. if you have long dives, you want to get out as much nitrogen as possible, on short dives you want as little helium as possible..
This is because He is a much faster gas than nitrogen.. so if you have a long BT and get saturated with nitrogen, it will take much longer to decompress than if you get saturated with helium..


On a 210" dive I'd personally only uses 25-35% Helium in the mix on most dives.. there really isnt the need for much more.. in this range a "heliar" mix comes in quite reasonable with a 30%He/ 15% oxygen mix (filling to 1000 psi helium before topping)
Fill with ~30% helium than top with air..

 

[Blackwood]

Yes, and I was working on a Commerical job in a Hard Hat back in December last year and we were doing 210' mixed gas on Heliox. Thats why I was asking. because it elliminates any nitrogen if I am correct.

Yes, Heliox is nitrogen-free. Of course, you are replacing the Nitrogen with an even lighter inert gas (will go in and come out of solution faster).

 

[D1V3R]

Heliox builds up faster then stops, making it good for really long dives, but air or trimix are better on short dives because they dont build up as fast

 

[wedivebc]

Now on CCR my understanding is you can still use nitrox or trimix correct?

CCR divers usually use trimix or air diluent. Using nitrox dil is pretty much a waste of time since you add O2 within the unit.

 

[PaulSmithTek]

I've seen both used on CCR.

Is there special Modifacations that you have to make?

 

[bruehlt]

I have heard talk that Heliox is starting to move the way that Nitrox did, back in the day (remember when Nitrox was considered a voodoo gas??!).

The only limiting thing that is preventing it from being used in recreational (and more technical) diving is the cost! The benefits of using it, as stated in a few other threads, are great for depths closer to 100 ft - but since Helium is not a gas that is very easy to produce, the price is the prohibiting factor, IMO.

 

[PerroneFord]

I am *NOT* a CCR diver. I said I have "seen" both used. Usually when the diver in question was not certified to use pure oxygen. In that case, using 40% or 50% nitrox. I know very little else about the process other than by using air as a diluent, you can control the ppO2.

 

[PerroneFord]

I have heard talk that Heliox is starting to move the way that Nitrox did, back in the day (remember when Nitrox was considered a voodoo gas??!).

The only limiting thing that is preventing it from being used in recreational (and more technical) diving is the cost!

From what I understand, Helium is also a bit more exacting when it comes to doing the decompression. You can't just blow up to 15 feet for a safety stop. That might also be a consideration for it's use by recreational divers. Lets face it. There are a number of recreational divers for whom a $35 tank fill isn't all that big a deal.

 

[D1V3R]

I am *NOT* a CCR diver. I said I have "seen" both used. Usually when the diver in question was not certified to use pure oxygen. In that case, using 40% or 50% nitrox. I know very little else about the process other than by using air as a diluent, you can control the ppO2.

you have to be certified to use pure oxygen? oops

 

[wedivebc]

you have to be certified to use pure oxygen? oops

He has no idea what he is talking about. You need a adv nitrox cert for CCR diving. Semi closed rebreathers use nitrox but you can NOT use nitrox in a CCR in place of O2 whether you are certified or not. It will KILL you. This guy Perrone Ford is posting garbage all over this board.