NITROX for any and all dives?

[boulderjohn]

It hasn't happened in this thread, but many people argue that with Nitrox, you can either have longer bottom times, or you can be safer--but you can't have both. Alex Brylske of Dive Training magazine says that regularly (or he did--I haven't read an issue in years). The idea is that if you have the gas for it, you can certainly extend your bottom time, and that is one choice. You can also dive nitrox on an air setting for safety reasons, and that is the only other choice.

As I have shown many times in similar threads, that is simply silly. The argument assumes that you will always dive to the end of NDLs on every dive. I have shown using tables in those threads that on a 2-tank dive, a diver using nitrox can get both significantly more bottom time and also be much farther from NDLs than a diver on air. You can even do it on a single dive. If you only go a few minutes longer than the air diver, you are getting more bottom time, and if you don't go near the nitrox NDL, you will also be farther away from NDLs.

 

[kelemvor]

It hasn't happened in this thread, but many people argue that with Nitrox, you can either have longer bottom times, or you can be safer--but you can't have both. Alex Brylske of Dive Training magazine says that regularly (or he did--I haven't read an issue in years). The idea is that if you have the gas for it, you can certainly extend your bottom time, and that is one choice. You can also dive nitrox on an air setting for safety reasons, and that is the only other choice.

As I have shown many times in similar threads, that is simply silly. The argument assumes that you will always dive to the end of NDLs on every dive. I have shown using tables in those threads that on a 2-tank dive, a diver using nitrox can get both significantly more bottom time and also be much farther from NDLs than a diver on air. You can even do it on a single dive. If you only go a few minutes longer than the air diver, you are getting more bottom time, and if you don't go near the nitrox NDL, you will also be farther away from NDLs.

Yeah, I like a lot of what he writes in his books, but obviously he hasn't got everything quite figured out with regards to nitrox.

 

[MaxBottomtime]

You are correct: it has not been proven that Nitrox makes some people feel less tired, nor has it been disproven. The anecdotal evidence is, however, tantalizing...

As a scientist you should know you can't prove a negative.

 

[tursiops]

As a scientist you should know you can't prove a negative.

I know what you meant to say, but you didn't actually say it.
You can only disprove something. But that something might be a negative or a positive.

 

[kelemvor]

I know what you meant to say, but you didn't actually say it.
You can only disprove something. But that something might be a negative or a positive.

According to some scientists, you can do neither in science. Common misconceptions about science I: “Scientific proof”

 

[Magnus Lundstedt]

Hard to get too far beyond 40% with a membrane I think.

Not so. This membrane system give ~93%


Philips - UltraFill Home oxygen system

 

[kmarks]

According to some scientists, you can do neither in science. Common misconceptions about science I: “Scientific proof”

That's just getting into semantics. Gravity is only a theory by the true scientific meaning. It's a pretty well supported one, though.

The daytime talk shows wouldn't have the same feeling if they said "All evidence suggests... you ARE the father!"

 

[tursiops]

According to some scientists, you can do neither in science. Common misconceptions about science I: “Scientific proof”

The fact that something (non-mathematical) cannot be rigorously disproven, for all circumstances and all time, is hardly the issue. The issue is that you can come much closer to disproving than you can to proving. All it takes is one trial that violates my hypothesis, and my hypothesis is dead meat. Disproved. But to prove my hypothesis, I would never have enough trials, because I'd have to test them all. We could agree that 1000 trials is enough? 10,000? There is no end.

 

[mi000ke]

Six bucks is a beer or more! I'm CERTAIN the beer will make me feel better than the nitrox.

Fortunately it's not either or. (And can get 2 Caybrews for that six bucks!)

 

[Steelyeyes]

My 2 PSI:

Given enough gas, you can choose to extend bottom time or alternatively (theoretically) reduce your DCS risk at the same bottom time using Nitrox. At depths where you will be nowhere near a deco obligation anyway because gas is the limiting factor in bottom time, you're just spending money for little to no benefit.

On our last trip to Cozumel my wife and I used Nitrox in 100 cf Al tanks for every dive. Most of the people we were diving with did the same except the last day. That day we were diving the east side of the island and were paired with a couple with the same tanks but filed with good old air. The couple turned into a single after the first dive because one of them was seasick and was dropped on the beach. The last dive of three was 60 FSW the whole time. About 30 minutes into the dive the DM took the air diver up to 30 FSW and followed above us. At 70 minutes or so Mary and I terminated the dive because we were getting cold and the other diver had to be damn bored by then, we still had time left to our NDL and we had about 1200 psi in the tanks.

So in certain situations where your NDL limits you more than the gas supply Nitrox markedly extends your bottom time. Other times not so much. We think it's worth the money most of the time but other people's mileage may vary.