why hasnt nitrox replaced compressed air completely?

[MXGratefulDiver]

For me, EAN32 is what I dive about 95% of the time ... at home because it's so suitable for the depths and profiles I like to dive, and on vacation because I enjoy not having to push my nitrogen loading limits.

One of my favorite profiles at my local mudhole can easily put me over NDL even on EAN32 ... and only doing the one dive per day. Sometimes I'll be joined by someone who brings an air tank, and we either have to cut the dive short or make sure we ascend with adequate gas to spend 10-15 minutes between 20 and 10 feet while he clears deco.

It really depends on the diver. For those who dive occasionally, or who tend to go through their breathing gas quickly, nitrox often doesn't offer enough of an advantage to be worth the expense. For those who dive a lot, or who have excellent gas consumption rates, or who spend a lot of time in the 60-100 foot depth range, it offers significant advantages.

... Bob (Grateful Diver)

 

[alewar]

Where I live there is a strong culture of people creating or joining small non-profit diving clubs. The pride of these clubs is the small compressors they keep in some basement where their members and friends can go and fill their cylinders by themselves for free. Recreational diving around here is a social activity with a barbecue-to-dive ratio approaching one. People do a couple of short dives on the weekends and eat and drink something together. There is no way for most of these clubs to afford a continuous blending station and filling by partial pressure isn't worth the risk for the clubs. That's why Nitrox isn't all that popular in Germany.

 

[iluvtheocean]

other factors besides training issues can be permit issues for the shop... Air is cheaper than nitrox whether it's hyper-filtered or not... whether it's going to be offered depends on the where it's getting filled ---
for example - Looe Key doesn't offer nitrox that i'm aware of -- why not? cause most of their dives off the reef are 15 feet or less and their boats also cater to the snorkelers... so doesn't make sense to offer.


it's also supply vs demand. Demand has to be high enough for someplace to offer it so they can make a profit. Liveaboards can figure the cost into your tab.

 

[TN-Steve]

Quick Question.... I know Nitrox has an enriched O2 content, and the lower Nitrogen level leads to the longer NDL limits. Is your 'rate of consumption' the same for Air and Nitrox? I would think that it would be, and just putting numbers here for demo, a diver that got 60 minutes from a 80cf tank of AIR at 45 feet before hitting 500psi remaining would also get 60 minutes at 45 feet with EAN 32 before hitting 500 psi.

You are breathing the same volume of GAS no matter what, so the tank would drain at the same rate, correct? I can see where the benefits come in in terms on NDL, but having 50% more oxygen in your mix doesn't figure to a 50% reduced consumption rate.

Thanks,

Steve

 

[String]

We were asked by the regional management about the viability of offering free nitrox. We did the maths and for us it wasn't.

Accounting for filters, electricity and everything we worked out an air fill cost us roughly £1.

Nitrox by the time we refill the Js of O2 and the extra time, tank cleaning and so on we worked out £3.50. That was without the initial outlay for blending panels, valves, replacement O2 sensors and so on.

So 3.5x the cost to us as a business to offer Nitrox vs Air. As the benefits for the customer were exactly zero we didn't bother.

 

[Basking Ridge Diver]

Quick Question.... I know Nitrox has an enriched O2 content, and the lower Nitrogen level leads to the longer NDL limits. Is your 'rate of consumption' the same for Air and Nitrox? I would think that it would be, and just putting numbers here for demo, a diver that got 60 minutes from a 80cf tank of AIR at 45 feet before hitting 500psi remaining would also get 60 minutes at 45 feet with EAN 32 before hitting 500 psi.

You are breathing the same volume of GAS no matter what, so the tank would drain at the same rate, correct? I can see where the benefits come in in terms on NDL, but having 50% more oxygen in your mix doesn't figure to a 50% reduced consumption rate.

Thanks,

Steve

Correct - even though I am not Nitrox Certified - I can answer that question for you...

 

[Keith.M]

Quick Question.... Is your 'rate of consumption' the same for Air and Nitrox?

Yes, it is the same. Just different percentages of nitrogen and oxygen.

I tend to only use it when the dive(s) warrant it.

The best example I can give was when I was in San Diego last year to get wreck certified. We were doing 3 dives each day, (2 days)

We did one dive on the Ruby E. (max 85 fsw) and 2 on the Yukon (max 105 fsw) the first day. Then all three on the Yukon the second day.

I was diving 32% for all of them. The first day I was in a 3 person team and we were matched pretty well regarding consumption and our gas and NDL matched pretty well too.

The second day, I was matched with another diver that just joined us for the day. He was last minute and had not been able to reserve Nitrox so he was on air.

Our first dive went OK and we matched up pretty well. On the second dive though, after a very short amount of bottom time, he started signaling me very agitated. He was flipping off his computer and signaling to me that he had 1 minute of NDL left. This was only his second dive and I had 2 this day and three the day before. I still had 16 minutes of NDL left. I gave him a pat on the shoulder, an OK and a thumb up.

He felt really bad about it, but in reality, this was the guy I had dived with on my first 2 post certification dives. He had been so kind and caring and was an excellent role model, that I had absolutely no issue about aborting this dive early.

But these type of dive profiles are really where you are going to see an advantage with nitrox.

 

[Jim Lapenta]

Nitrox also has some other risks when using it repeatedly day after day on multiple dive days. Steve Lewis in Staying Alive, and again in my Adv Nitrox and Deco Procedures Instructor class, talks(talked) about your CNS clock and keeping track of that when using elevated levels of O2 in your gas. For many people it's not an issue but it can become one since it's not an exact science and everyone's tolerance level is different. Especially on liveaboards where you don't have the decreasing levels of nitrox that happen over the week. Ya know the ones where they start to run low on O2 and now you're getting 30, 28, 26, or maybe less instead of the 32 you paid for. But then from what I am told some people don't analyze every tank like they should anyway. They just say ok I paid for 32 so I must be getting it.
If you don't know what I'm talking about with this you probably should not be using nitrox anyway.

 

[KeithG]

Right tool for the right job. as already noted, Nitrox has some additional procedural complexities and MOD limitations not present in air.and cost.

If you are doing many "fairly deep" square profile recreational dives on many consecutive days, then Nitrox can be the right tool. A live aboard in Turks & caicos comes to mind as the top of the reef is generally around 50 feet. No ability to do the last half of your dive in shallow waters.

But there are lots of other places where you can do "really deep" repetitive recreational dives with no need for Nitrox as you can do multi-level dives spending a significant portion of your dive in shallow waters. Like at bonaire.

Depending upon your needs Nitrox may be the right tool. For me, air is the right tool.

 

[DogDiver]

I haven't dove on air in over 15 years. We can vary the mix based on the planned depth. Actually in North Florida 32% banked Nitrox paid by the cubic foot is Cheeper than air based on flat rate. A set of double 120's usually costs me $15-$17 for a fill based on cost per cubic foot.


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