Will mixed gas use eventually extend recreational depths?

[Kim]

This is a theoretical question. I am not Trimix trained, but the availability of new 'Rec' Trimix courses make me wonder.

Recreational diving limits have always been governed by air AFAIK. However, presumably with the training now available for using Trimix at recreational depths the NDL for a given gas mix must be extending deeper. What do people think is the chance that this actually will have an effect on what is considered a recreational depth limit, i.e. a non-deco dive......decompression occuring during the ascent?
If it does - what would be a likely limit in the future?

 

[MikeFerrara]

I'm not sure what you mean when you say

However, presumably with the training now available for using Trimix at recreational depths the NDL for a given gas mix must be extending deeper.

I guess some would argue but depending on the model adding a little helium doesn't decesarily extend no-stop time/depth. Using a haldanian model you'll typically require staged decompression sooner with some He in the mix. I say that realizing that many believe that it's a better gas to off gas.

 

[MB]

If the cost of He could be reduced (or stay the same as other costs rise), I think a couple of "standard" mixes would become quite common for deeper recreational uses. There really isn't any rational reason to diving in the deeper recreational range on air if the cost of tri-mix could be contained. Nitrox for 100' + gives only a minimal edge when compared to other simple mixes. Within the next 15 years dives deeper than 90' could all be on mix.

As for extending the depths of recreational dives, I doubt that it will become too common for the diving masses to dive below 130'. Given the removal of the N2 disadvantages by using mixes, the biggest disadvantage remains air supply and consumption, and the need for redundant (and expensive) equipment to safely return home from these depths. So while tri-mix will make current depth limits more accessible and safer, I doubt that it will extend the depths significantly for most recreational divers given the air consumption issues.

 

[Randy43068]

I hope so, but I think the cost of Helium prevents it from being that mainstream.

 

[Diesel298]

Helium absorbs into your bidy faster than nitrogen..
so its not gonna extend your NDL times. its a whle different thing

its not hard, but theres some new stuff to learn

 

[String]

NEar term, trimix is the way to go but the main thing stopping it becoming "routine" is its enourmous (and increasing) cost. Its out of reach of a lot of divers. Until they find a new way of actually extracting the stuff its going to remain expensive.

Yes it does have issues (totally different on and off gas profiles and so on) but nothing major. Its just "different". As someone has already said, it wont extend NDLs, it could in fact reduce them.

In addition to this in medium term, 10 years or so in the future i see closed cicruit rebreathers becoming far more common and pushing into the sport diving market considerably more so than now.

 

[Kim]

Well I guess I'll have to do a course to really understand this as I admittedly don't know anything about the real on-gassing/off-gassing speed of helium - except that it's 'faster'. Maybe my theory is a little screwy here because I was assuming (probably a bad thing!) that helium would off-gas fast enough during a slow ascent to not really be a factor given that it's a lighter gas than nitrogen.
Out of interest then - if helium IS a factor that will decrease an NDL at say 38 meters - what is the real benefit of diving such a mix? Simply that helium doesn't get you narked?

Of course the gas consumption issues are another thing....I get that!

 

[MikeFerrara]

As helium gets more popular so will rebreathers. Why throw away perfecrtly good helium?

kim, there are several advantages. The reduction in narcosis, reduced breathing resistance because of the lower density which in theory further reduces narcosis and tox risks due to less CO2 build up. Now, what does that mean to you at 100 ft? the deeper you go the easier it is to see a real advantage.

 

[Randy43068]

I miss read the heading of the thread...
No, it won't extend NDLs. Sorry..

 

[padiscubapro]

As helium gets more popular so will rebreathers. Why throw away perfecrtly good helium?

kim, there are several advantages. The reduction in narcosis, reduced breathing resistance because of the lower density which in theory further reduces narcosis and tox risks due to less CO2 build up. Now, what does that mean to you at 100 ft? the deeper you go the easier it is to see a real advantage.

Mike I would not cound reducing otox risks as a benefit of helium..In fact studies have shown quite the opposite..
It is true that helium makes ventillation easier and will reduce Co2 which IS a factor in causing otox, but the helium itself appears to lower the bodies resistance to otox, or more correctly, doesnt increase the tolerance (too tox) like n2 does..