Why Nitrox

[OE2X]

Thank you for your responses. I have a question about on of the earlier posters who mentioned oxygen toxicity at deeper depths with Nitrox. I will give you a little background so you get an idea where I am coming from. I really enjoy diving wrecks (not necessarily penetration) and taking my time exploring them and also learning the history behind them. In Canada where I mostly dive, a lot of the most preserved wrecks are in deeper water (100 - 130'). SAC rates aside, will Nitrox allow me to spend more time at these depths?

Yes. At 100' on air NDL is 20 minutes. On 32% it's 30 minutes.

 

[DandyDon]

Thank you for your responses. I have a question about on of the earlier posters who mentioned oxygen toxicity at deeper depths with Nitrox. I will give you a little background so you get an idea where I am coming from. I really enjoy diving wrecks (not necessarily penetration) and taking my time exploring them and also learning the history behind them. In Canada where I mostly dive, a lot of the most preserved wrecks are in deeper water (100 - 130'). SAC rates aside, will Nitrox allow me to spend more time at these depths?

Request 28%.

 

[espenskogen]

Thank you for your responses. I have a question about on of the earlier posters who mentioned oxygen toxicity at deeper depths with Nitrox. I will give you a little background so you get an idea where I am coming from. I really enjoy diving wrecks (not necessarily penetration) and taking my time exploring them and also learning the history behind them. In Canada where I mostly dive, a lot of the most preserved wrecks are in deeper water (100 - 130'). SAC rates aside, will Nitrox allow me to spend more time at these depths?

Yes it will, but you will need to operate with a relatively lean nitrox mix. For a 40 meter dive (roughly 130') at a partial pressure of 1.4 PPO2 (Which is the recommended pressure for the working portion of the dive), you can use a 28% mix. This reduces the N2 exposure by a little less than 10%, (Normal exposure fN2 79% - Current exposure fN2 71%) which will give you a little less narcosis and a little more bottomtime. It will effectively be like diving to 36 meters in terms of N2 absorbtion

Now, combine this with a rich mix for deco, and you're on to something.

E

 

[HowardE]

Thank you for your responses. I have a question about on of the earlier posters who mentioned oxygen toxicity at deeper depths with Nitrox. I will give you a little background so you get an idea where I am coming from. I really enjoy diving wrecks (not necessarily penetration) and taking my time exploring them and also learning the history behind them. In Canada where I mostly dive, a lot of the most preserved wrecks are in deeper water (100 - 130'). SAC rates aside, will Nitrox allow me to spend more time at these depths?

Yes. here's a link to a PADI EANx 32 Dive table... You'll notice the times in comparison to your air table. http://www.finpivot.com/eanx32dp.htm

 

[Pyrofish]

Now, I've not seen or felt that? O2 is also narcotic, so where did you get this.

The only time I have every truly noticed narcosis (I keep in mind that it's there and working to a degree anytime I go to any depth) was an Ooops! dive off of Utila, and that slammed me. Took a little dip to test the feeling, hit it, totally missed my turn depth with the feel-good feeling, scarey. :11: And caught all kinds of hell from the other divers who had never made a mistake!!

But I've been to 100+ on air and Nitrox both many times without feeling it - so where did you get that idea?

I noticed on AOW dive to 108', I was defintely narc'ed. No doubt. On my nitrox class dive we went to the T-bolt at 117' on 28% and felt no difference. There was another diver with us on air, she got narc'ed and she had us call the dive. Now, when I got back to reality, or 'not the keys' as I sometimes call it , I was telling the story to my buddy who is a deep diver. He told me that I probably would have been narc'ed too, if not for the nitrox. I hadn't even thought about that, so I looked around and saw it in several places listed as a benefit of nitrox. All I know, I wasn't narc'ed and that was the deepest I had been, and the longest I had been there. I know that nitrogen narcosis is unpredictable, but the anecdotal evidence seemed to add up to what I was reading.

Just my very limited experience and what I was told
Jason

 

[OE2X]

The two dives that I was the most narced on, were just down to 60'-70' and both were on 32%. The main reason on both dives were fatigue and being dehydrated.
Frankly I'm not convinced that you don't get just as narced on nitrox as you do on air.

 

[Walter]

I noticed on AOW dive to 108', I was defintely narc'ed. No doubt. On my nitrox class dive we went to the T-bolt at 117' on 28% and felt no difference. There was another diver with us on air, she got narc'ed and she had us call the dive. Now, when I got back to reality, or 'not the keys' as I sometimes call it , I was telling the story to my buddy who is a deep diver. He told me that I probably would have been narc'ed too, if not for the nitrox. I hadn't even thought about that, so I looked around and saw it in several places listed as a benefit of nitrox. All I know, I wasn't narc'ed and that was the deepest I had been, and the longest I had been there. I know that nitrogen narcosis is unpredictable, but the anecdotal evidence seemed to add up to what I was reading.

Just my very limited experience and what I was told
Jason

What you feel is not the best indication of impairment. You wouldn't believe the number of times I've heard people say they weren't narced on deep dives on air simply because they felt no different. The same applies to nitrox. I've also see reduced narcosis listed as a benefit of nitrox. If only it were so. Don't take my word for it, look it up in the NOAA Diving Manual.

 

[clarktenk]

It's the placebo affect. The only double blind study conducted to date showed absolutely no difference between air and nitrox.



That's a myth.

Sorry Walter but the reason they feel better diving nitrox is not a placebo effect. It's a direct result of having to offload less absorbed nitrogen into the tissues. Hence the reason for using nitrox. So since the body doesn't have to work as hard the divers come out feeling better when compared to a similar dive on air.

You are right on about the narcosis though. The O2 is just as narcotic as the nitrogen and some would argue more so. So there is no benefit to increasing the O2 from a narcosis stand point.

 

[DandyDon]

Sorry Walter but the reason they feel better diving nitrox is not a placebo effect. It's a direct result of having to offload less absorbed nitrogen into the tissues. Hence the reason for using nitrox. So since the body doesn't have to work as hard the divers come out feeling better when compared to a similar dive on air.

You are right on about the narcosis though. The O2 is just as narcotic as the nitrogen and some would argue more so. So there is no benefit to increasing the O2 from a narcosis stand point.

That is my much less educated understanding.

 

[Walter]

Sorry Walter but the reason they feel better diving nitrox is not a placebo effect. It's a direct result of having to offload less absorbed nitrogen into the tissues. Hence the reason for using nitrox. So since the body doesn't have to work as hard the divers come out feeling better when compared to a similar dive on air.

Upon what do you base that belief?