What's the deal with the "Advanced Nitrox" certification?

[jtivat]

You and I seem to be miscommunicating.

Run V-planner for TMX 30/30 and NO DECO GASSES, and compare it with EAN 30 AND NO DECO GASSES.

Then let's see what you get.

Well there it is!! You do dives like this and don't use deco gas??? That would explain a lot!

 

[Reg Braithwaite]

Well there it is!! You do dives like this and don't use deco gas??? That would explain a lot!

At the risk of pandering to the OP, who is interested in "Recreational" Diving (surely he will wake up to the fact that while it is possible to perform a dive with no mandatory deco on He, the expression "Recreational Trimix" is an oxymoron)...

How about somebody compares no-deco tables for EAN30 to no-deco tables for 30/30. What is are the NDLs for various depths? Is one shorter or longer than the other or are they the same? How do the RNT for various dives compare?

This might break the "deco gas impasse."

 

[jtivat]

At the risk of pandering to the OP, who is interested in "Recreational" Diving (surely he will wake up to the fact that while it is possible to perform a dive with no mandatory deco on He, the expression "Recreational Trimix" is an oxymoron)...

How about somebody compares no-deco tables for EAN30 to no-deco tables for 30/30. What is are the NDLs for various depths? Is one shorter or longer than the other or are they the same? How do the RNT for various dives compare?

This might break the "deco gas impasse."

If you run times on V-Planner with EAN30 and 30/30 you get 10 minutes of no-deco time with both. I am not going to do this for every ten feet but I bet they are with in one minute at any given depth.

This is at a +3 cons.

 

[nereas]

Does anybody in the real world actually use tables like these?

Seems kind of pointless when V-planner,decoplanner etc. exist and work so well.

Exactly!

 

[nereas]

If you run times on V-Planner with EAN30 and 30/30 you get 10 minutes of no-deco time with both. I am not going to do this for every ten feet but I bet they are with in one minute at any given depth.

This is at a +3 cons.

I on the other hand would bet that you run a greater risk of DCS with the use of TMX 30/30 as a backgas mix when you could just as easily use EAN 30 instead. Thus the TMX 30/30 is an unnecessary risk. Fine for deco in the range of 140 to 80 ft, but bad for "recreational" anything.

 

[orange_diver]

not if you believe helium on-gasses and off-gasses faster. which it does.

but i do agree that its a recreational waste, just on financial terms. i would definitely use 30/30 or 25/25 if i was penetrating a wreck even at 80' in cold or dark water.

 

[Reg Braithwaite]

I on the other hand would bet that you run a greater risk of DCS with the use of TMX 30/30 as a backgas mix when you could just as easily use EAN 30 instead.

Possibly.

Thus the TMX 30/30 is an unnecessary risk.

Does not follow logically from your first statement alone. If you believe that being narced magnifies the risk of some other event hurting or killing you, then you are actually evaluating a trade-off between the risk of DCS from mismanaging your ascent and the risk of narcosis impairing your ability to handle some less likely but possibly more catastrophic event.

It is entirely reasonable to feel that it is not a benefit for you based on your perception of your own ability to solve problems while diving EAN30 at certain depths vs. your perception of your ability to manage your ascent properly. However, I do not think that an increased risk of DCS in and of itself is sufficient reason to argue against the use of 30/30 as a breathing gas at depths where you could use EAN30.

I suspect this argument holds for both no-decompression and decompression dives in such ranges.

 

[Reg Braithwaite]

not if you believe helium on-gasses and off-gasses faster. which it does.

but i do agree that its a recreational waste, just on financial terms. i would definitely use 30/30 or 25/25 if i was penetrating a wreck even at 80' in cold or dark water.

Shipwrecks in moderate to cold water with medium visibility and some darkness is often the game up here in Ontario. Furthermore, even a no-deco dive can involve some task loading. For example, when diving wrecks in the Thousand Islands, you have to manage a current, sometimes the wreck gets silted out by divers with poor finning techniques such that you cannot see your way back to the mooring line, and if you are not able to ascend the line you must do a drift ascent and SMB deploy into boat or full-scale shipping traffic.

This kind of thing is routine for tech divers, of course. I am just pointing out that even without wreck penetration keeping your wits about you is critical. That being said, most of those wrecks are accessible with EAN32, but there are a few where I would at least wonder if 30/30 or 25/25 would be a good choice.

Which is why I'd like to look into some training. The advice here is outstanding, and I love how you guys are straight shooters. But ultimately I need to sit down with a∂ n instructor and/or a mentor and get in the water with some He.

It could well be that my training dives are the only ones I ever do with trimix. Shrug. That can't hurt.

 

[nereas]

not if you believe helium on-gasses and off-gasses faster. which it does.

but i do agree that its a recreational waste, just on financial terms. i would definitely use 30/30 or 25/25 if i was penetrating a wreck even at 80' in cold or dark water.

I completely agree with your post.

And if I were penetrating a wreck in the range of 100 to 140 ft, then I too would definitely use TMX 30/30.

I do happen to believe that helium on- and off-gasses faster than nitrogen, and thereforeI view it as a hazard for open water divers, who might lose control of their ascents and pop to the surface, and with TMX 30/30 that could definitely give them DCS. Even good divers are at risk of sometimes losing control of their buoyancy, such as due to a power inflator malfunction, or a swift upcurrent, etc.

 

[nereas]

Possibly.



Does not follow logically from your first statement alone. If you believe that being narced magnifies the risk of some other event hurting or killing you, then you are actually evaluating a trade-off between the risk of DCS from mismanaging your ascent and the risk of narcosis impairing your ability to handle some less likely but possibly more catastrophic event.

It is entirely reasonable to feel that it is not a benefit for you based on your perception of your own ability to solve problems while diving EAN30 at certain depths vs. your perception of your ability to manage your ascent properly. However, I do not think that an increased risk of DCS in and of itself is sufficient reason to argue against the use of 30/30 as a breathing gas at depths where you could use EAN30.

I suspect this argument holds for both no-decompression and decompression dives in such ranges.

The danger from being narked is that you snag and snap your cave line inside the wreck.

The danger of diving with helium when you don't really need it is the added risk of DCS from an uncontrolled ascent.

Like everything else, you need to weigh the 2 risks.

Generally speaking, if nitrox alone works, instead of helium, I use nitrox.