Diving on EANx... Air Consumption vs. Nitrogen Absorption At Different Depths?

[ElectroPulse]

Hello, all!

I finished my Basic OW with PADI a week ago, and have been thinking about what I want to do in the future.

Where I am going to be diving, the price for a day of diving is the same whether it is on air or EANx. Because of this, I have been thinking about getting my EANx cert right out of the gate, before I even go on a regular dive.

After doing a bit more thinking about my 4 dives during OW training, I remembered that the limiting factor was air in our tanks. I don't remember what the NDL time remaining was, but I know it was a LONG time after our tanks were low. However, this was at a maximum of 60 feet of depth.

Generally, at what depth does the limiting factor change from air capacity to nitrogen absorption?

I am trying to determine whether I want to spend the money on that at this point or not... I figure the earlier I get it the more benefit I will get out of it (especially since EANx is essentially "free"), but if I won't get any benefit from it, I'm not sure whether I'll get it now or not...

Thanks!
ElectroPulse

 

[TSandM]

You will always get a benefit from it -- no matter what dive you do, you will have less nitrogen at the end of it on Nitrox than you would if you did the same dive on air. Less nitrogen is at least theoretically beneficial, even if it is difficult to prove (since DCS is so rare in the recreational dive spectrum to begin with).

Your question really can't be answered, because gas consumption is both individual and changes with time. New divers almost always blow through gas, and use fairly small tanks. As you gain experience, your gas consumption will drop, and many of us invest in our own tanks, which are generally larger. At some point, you will be able to stay down long enough to approach your NDLs. In general, Nitrox is most useful for dives in the middle of the recreational range, between 60 and 100 feet. Because of oxygen toxicity, you have to decrease the oxygen content of the gas as you go down, which means that below 100 feet, you are buying little additional bottom time. Above 60, the NDLs are long enough that most folks will hit gas limits before going into deco.

But there is another benefit to Nitrox, which is where you are doing multiple dives per day. Nitrox will reduce your cumulative nitrogen loading at the end of the day, or the end of a week-long trip.

 

[kelemvor]

DO IT.

You might not get benefit from the extended NDL's due to air consumption. However, I (like many others) feel better after diving nitrox. I don't feel tired or worn out after diving nitrox like I do after two tanks on air. If you can dive nitrox for no extra charge you should jump all over the certification.

Not to mention, even if you're not nitrogen limited you'll just be giving yourself an even greater margin of safety when diving nitrox vs air.

 

[Doc Harry]

Generally, at what depth does the limiting factor change from air capacity to nitrogen absorption?

Very intelligent question. Generally deeper than 60-80 feet. Check your NDL tables for your answer.

 

[bracko]

^ well NDL's are a hard target while a new diver will have a drastically reducing SAC. If/when you have a stable SAC a short calculation & graph in MS excel would most likely give you your answer. and this obviously assumes a bounce dive which rarely happens on reefs.

If you are actually located in Palau I would strongly advise doing the Nitrox course seeing as it's no more expensive than diving on air.

 

[ElectroPulse]

Thanks for the replies!

Ok, looks like I'll definitely be doing it as soon as possible. I had been wanting to, but wasn't sure how much of a tangible benefit there would be to start with.

And yes, I'm currently located in Palau (gonna be here until the end of May)

 

[bracko]

Very jealous. definately go for NITROX.

 

[MaxBottomtime]

Once you get your Nitrox text material you will read that the "feel better" syndrome is a placebo, and as Lynne mentioned the safety factor is so small because the rate of DCS is already so low. If it doesn't cost any more than air you might as well use it, but the real benefit of Nitrox is longer available ndl and/or shorter surface intervals. As a new diver you will probably not come close to your ndl unless you are making several dives per day.

 

[ElectroPulse]

Once you get your Nitrox text material you will read that the "feel better" syndrome is a placebo, and as Lynne mentioned the safety factor is so small because the rate of DCS is already so low. If it doesn't cost any more than air you might as well use it, but the real benefit of Nitrox is longer available ndl and/or shorter surface intervals. As a new diver you will probably not come close to your ndl unless you are making several dives per day.

Hmm... That last part I'm wondering about. My diving will probably mainly consist of diving for one day on a weekend, with a maximum of 3 dives (usually 2, though). Would I see any benefit with that? (or that much?)

 

[mala]

Hmm... That last part I'm wondering about. My diving will probably mainly consist of diving for one day on a weekend, with a maximum of 3 dives (usually 2, though). Would I see any benefit with that? (or that much?)

if you are looking for longer bottom time on repetitive dives then there will be a benefit.
depends on gas consumption and depth of course-the first dive may still be gas limited but the following dives especially if they are past 25m are likely to have longer ndl's .