Why Nitrox

[OE2X]

The main benefit is the reduction of nitrogen loading. This can minimize your DCS risk.

 

[espenskogen]

The bit about the equipment is a little misleading. For Nitrox 1, which is 40% O2 and below (IIRC), you only need a special tank, or the tanks you're usuing to be O2 cleaned. The rest of your gear, provided your computer is Nitrox compatible, will remain the same. If you go on to nitrox 2, I believe that's a different story.

Believe this bit is actually a bit misleading in itself.

Nitrox 1 is usually a reference to 32% nitrox or EAN32.
Nitrox 2 is usually a reference to 36% nitrox or EAN36.

These are two standard mixes, which PADI amongs others produce tables for. I believe ANDI was one of the first agencies to define these - And they called it SafeAir.

For rich O2 mixes (41% - 100% O2), you will need :

Advanced Nitrox training (Available from TDI/IANTD/ANDI and others)
O2 clean equipment

If you dive on nitrox in an area where they use partial pressure blending (Which means they start with filling the tank with 100% O2, and then top up with air) then your tanks and tankvalves need to be O2 clean, even if you dive with nitrox leaner than 40% - I.e all hydrocarbons need to be removed, and a water based lubrication need to be used.

For Membrane mixes or premix this isn't actually that important, but many locations use O2 clean tanks anyway, if for no other reason not to confuse us poor divers, who might not understand the principles behind gas blending.

Hope this helps.

E

 

[IXΘYΣ]

NOAA defined those mixes. Their "proper" names are "NOAA Nitrox I" and "NOAA Nitrox II."
Hi, by the way.
IXΘYΣ

 

[RumBum]

I am reading the study book right now.
Benefits:
stay underwater longer, shorter surface intervals, longer repetitive dives, less fatigue, (depending on your profiles) less chances of decompression sickness
Disadvantages:
shallower depth limits, possibility of oxygen toxicity to keep up with, more to learn, you may need some different Nitrox compatable equipment, and Nitrox tank fills cost more than air.

Essentially, if you are planning on doing a vacation dive with 4 or 5 dives a day for several days then you should probably get Nitrox certified. That is where diving Nitrox will really make a big difference. (IMO)

 

[Walter]

Nobody knows why, But I just feel better after a dive with Nitrox than doing the same dive with air....

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

It also affects the depth at which you get narc'ed.

That's a myth.

 

[espenskogen]

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?

He's actually entirely correct.
The experience of narcosis is far more common on deep dives - i.e beyond 100 ft. You typically start to experience narcosis around 100', but it really kicks in around 130' - 150'.
There are people who start feeling narked from 80' down, but certain researchers have claimed that the feeling of nitrogen narcosis is only really affecting a diver from beyond 100'. This of course is disputed, but the theory from these researchers were that because divers are taught that they should start feeling narked on dives deeper than 18 meters, many do.

Now, O2 is mildly narcotic, but the effect of O2 narcosis only comes into effect at high partial pressures. So you might experience it a bit at a PP02 of 1.6 or higher, but it is far less narcotic than Nitrogen - Probably more on par with Helium, in fact.
For a detailed reference on this read: http://www.ncbi.nlm.nih.gov/entrez/...ve&db=PubMed&list_uids=10849687&dopt=Citation

It bascially concludes at at a PP02 of 3.0 ATA, they cannot conclude that O2 has a narcotic effect. This is not to say that it DEFINATELY has no narcotic effect - But scientists cannot prove that it DOES have any narcotic effect.

So by reducing the nitrogen loading, you achieve reduced narcosis, and reduced risk of dcs. Of course, the real benefit is the dcs risk reduction, which is why you feel less fatigued diving a recreational profile on nitrox than air. (There are people who believe the fatigued feeling is actually a symptom of subclinical dcs, and that a lot of recreational divers routinely 'bend' themselves without even realising it. - Only way to verify that, I suppose, is trying to dive more conservatively, and see if you feel less fatigued. For more detail on this, have a look at the WKPP project : http://www.wkpp.org/articles/Decompression/min_deco.htm )

 

[espenskogen]

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.

Totally disagree with you Walter.

The difference is that a lot of divers do incomplete deco on recreational profiles - Be that rapid ascent or too short safety stops or whichever. This incomplete deco makes you feel sluggish and fatigued. Nitrox, reducing the N2 loading, and increasing the gradient during deco, helps alleviate this. You can particuarly feel this difference if you do a deep dive (120' or so for 10 minutes), spend 10 minutes on 6 meters on 80% nitrox as opposed to doing the same thing on air. I bet you, on air you'd feel like you've been running a marathon, whilst the 10 minutes on 80% would make you feel like a proverbial superhero.

On the other hand - If you do a proper superconservative ascent on air, and a 1'/minute ascent the last 33', and an adequate safety stop AND you're well hydrated, then you might not feel any difference. Once you're sufficiently deco'ed, you won't get any added benefit from further deco.

 

[Footslogger]

For me it was primarily the lower nitrogen loading/absorption. The wife and I typically go on one liveaboard dive trip a year (more if we can) and generally get in about 30 or more dives during the week. We don't necessarily dive deep, but occasionally will drop down on a wall (on purpose and by accident). I do photography so the added bottom time is a benefit but at the shallower depths that was never really a huge issue.

I don't notice any difference in how I feel after a nitrox dive as compared with regular air. My diving style is pretty casual and non-strenuous anyway.

After 30+ years of diving I just felt like it was time to take a course and the Enriched Air Diving package was offered on a liveaboard last year ...so we said, why not !! Ended up costing us more than the course because our old computers were air-only and if we wanted to continue diving Nitrox we needed to either rent or buy new ones. We picked up a couple Gekkos and now dive Nitrox routinely.

'Slogger

 

[Daner]

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?

 

[Fish_Whisperer]

You lucky dawg.... I've seen some breathtaking photos of wrecks in the St. Lawrence River. Very cool. Good luck!