Pros and Cons of Nitrox: What are they?

[H2Andy]

there is a reduction in being fatigued, as in being less tired after multiple dives or multiple days of diving due to less off gassing.

the official word on this is that there is no proof of it being so.

however, there is a lot of annecdotal evidence (myself included)
that you do FEEL a lot better at the end of the day.

i think it might be just too early to tell. there's not enough
evidence in.

 

[glbirch]

Mike,
I really didn't want to restart this discussion, but since you asked:

1. The accident rates are from the DAN 2004 report, but you'll need to make some calculations (number of nitrox accidents/number of nitrox users). I realize that this is not the primary intent of these numbers and that there are other factors involved in this. I personally believe that Nitrox, when used properly is as safe as air. What I do not believe (at least not until I see proof) is that it is safer than air, which I hear some people claim.

So, from the Dan 2004 Report, Figure 7.1, slightly over 70% of the PDE group used air but they accounted for over 80% of injuries and around 75% of fatalities. I'd be interested in your calculations.

 

[ScubaRon]

Actually Ron, Mares' statement reads "Mares regulators and octopus are designed and intended for use only with clean, compressed atmospheric air." "Do not use this equipment with any other gas or enriched air."

The reason for that is because Mares markets a nitrox version of their regulators, and this statement is intended to incite the owner to purchase the nitrox dedicated regulators. I have a V16 epos and an MR12 Axis, both of which are in their standard configuration, and I use nitrox exclusively with these regulators without any problems.

Don't know much about aqualung (other than the Titan LX is certified from the manufacturer for mixes of up to 40%), or atomics, but it seems both manufacturers mimic Mares.

Rick

Rick,
Nitrox compatibility has nothing to do with the ability to switch back and forth between standard air and nitrox. It simply means that the materials of the reg do not deteriorate due to the higher O2 percentage.

I just called my buddy with a Mares Surveyor Nitrox and he confirmed that the manual has a warning that when switching from air to nitrox the device needs to be O2 cleaned.

I seriously doubt that Mares puts that warning in the manual to get you to buy another reg. It would give them a strong competitive disadvantage. I would be suspicious that the reg contains materials that deteriorate in higher O2 environments. I would ask the tech next time your reg serviced.

 

[DoUDive2]

I've been told numerous times that there is a reduction in being fatigued, as in being less tired after multiple dives or multiple days of diving due to less off gassing.

Annecdote: I'm less fatigued when I dive an air computer using nitrox.

Hypothesis: I suspect that I would be more fatigued if I dove a nitrox computer using nitrox.

Reference: Dive an air computer using air.

Chris

 

[ScubaRon]

So, from the Dan 2004 Report, Figure 7.1, slightly over 70% of the PDE group used air but they accounted for over 80% of injuries and around 75% of fatalities. I'd be interested in your calculations.

Actually it was the 2003 report I used and the numbers there were that 11% of the PDE divers used nitrox and 12.7% of the injuries used nitrox. Compared with the "air" divers that was a 19% higher accident rate.

Looking at the 2004 report these numbers are indeed quite different and in favor of nitrox. The difficulty with this comparison is that the injury numbers are from a different population than the PDE numbers. Looking at the enormous growth of nitrox among PDE divers, I wonder if there is not a strong bias here...

 

[glbirch]

Actually it was the 2003 report I used and the numbers there were that 11% of the PDE divers used nitrox and 12.7% of the injuries used nitrox. Compared with the "air" divers that was a 19% higher accident rate.

Looking at the 2004 report these numbers are indeed quite different and in favor of nitrox. The difficulty with this comparison is that the injury numbers are from a different population than the PDE numbers. Looking at the enormous growth of nitrox among PDE divers, I wonder if there is not a strong bias here...

As PDE divers are just volunteers from all over the place, I'm not sure what you would think the bias would be. The numbers just reflect the growing use of Nitrox in diving.

As an alternate possibility, the more recent survey is from a larger pool which should in theory provide more accurate numbers. Also, it's possible that there is a better understanding of Nitrox and it's proper use than previously, and thus less problems. It will be interesting to see the 2005 report.

Still not sure how 11% use and 13% injuries becomes a 20% higher accident rate.

Edit: I notice that of the 2001, 2002, 2003 and 2004 reports, three of them show Nitrox as the group with much lower accident rates. Only one year (2003, the one that you choose to quote from) shows Nitrox with (slightly) higher accident rates. Wonder where the bias is?

 

[grazie42]

DoUDive2 once bubbled:
Hypothesis: I suspect that I would be more fatigued if I dove a nitrox computer using nitrox.

I suspect this would be true as well IF you used up ALL your allowable bottom-time on nitrox. For me, personally, getting closer to the air-limits on a single tank dive is a lot easier then doing the same on the nitrox-limits and so even diving nitrox on a nitrox computer I´m not as fatigued as I would´ve been on air...

I agree with all the other benefits of multi-day diving and generally less fatigue as well as the statement that "most" regs work below the 40% mark (check your reg-instructions and read between the lines).

SLIGHTLY OT:
Another benefit that isn´t covered in the course litterature in nitrox is the benefit of nitrox as a hangover cure. Now I´m NOT suggesting that you go diving as a cure for your hangover but that you simply breath nitrox while recovering (preferably in a horizontal position, always stay horizontal remember).
If you have "company" during your early recovery phase this may evoke some surprised exclamations from said "company". If their presence is temporary this is nothing to worry about (as you don´t much have to care about their oppinions) and if it´s not they may as well get used to it

Disclaimer:
The above is not intended to promote either nitrox as a hangover cure (well ok just a little bit) nor the presence of "company" (of any form) during any part of the process that leads to the recovery phase of a hangover (if you believe this...)

 

[MikeFerrara]

Mike,
I really didn't want to restart this discussion, but since you asked:


2. I agree with you on the benefit of nitrox in multiday repetitive diving, but considered this as part of the increased bottom time.

3. From the Atomic Aquatics user manual:
At time of purchase, you must decide if this regulator is to be used with EAN or standard compressed air. If you desire to use EAN, this product must be dedicated for EAN only and identified as such. Do not switch between EAN and standard compressed air, as compressed air may contain traces of hydrocarbons which could contaminate your regulator system with potentially flammable residues incompatible with EAN. If you use or test this regulator with compressed air, it must be re-cleaned before EAN use.
From the Aqualung user manual:
...if a regulator has had use with Grade E breathing air, it should receive a standard overhaul including ultrasonic cleaning with a detergent solution that removes hydrocarbons, prior to being put back into nitrox service.
Mares and others have similar statements.

4. Of course switching between O2 compatible air (which I presume you mean with "mod Grade E"...) and nitrox is no problem. But most standard air is Grade E, which is not O2 compatible. So repeated switching means repeated introduction of hydrocarbons, ergo repeated combustion. The question is how this impacts your reg in the long term and that is where facts lack and opinions differ.

Unless we work in a clean room we'll never have hydrocarbon free anything. The goal is clean enough. We assume there is a build up of contamination over time which is why we re-clean equipment that needs it every so often. A build up of hydrocarbons over time does not mean repeated combustion.

What they're not telling you is that the shops who pump a lot of nitrox are using some method other than partial pressure blending to blend it and all you're getting is normal grade E (as far as hydrocarbon content ) nitrox so there isn't any difference.

aqualung has always been full of it. It's an attempt to sell you more regulators. They now distribute apeks and apeks says no such thing so it appears that they can't make up they're mind. Reference any nitrox text or blending text that you want and the rule is that below 40% we don't worry. They then add the clause that you should follow the manufacturers recommendations. What we do is avoid the manufacturers that claim that you need to go through a lot of trouble for mixes below 40%.

Dedicated equipment isn't needed for mixes below 40% O2 with the exception of tanks or valves that will be filled by PP or some other method that introduces high FO2 gas (over 40%) in the process.

 

[MikeFerrara]

there is a reduction in being fatigued, as in being less tired after multiple dives or multiple days of diving due to less off gassing.

the official word on this is that there is no proof of it being so.

however, there is a lot of annecdotal evidence (myself included)
that you do FEEL a lot better at the end of the day.

i think it might be just too early to tell. there's not enough
evidence in.

This is an important point. The most important advances in decompression methods are being made on the basis of annecdotal evidence based on how divers feel. reference some of BRW's (and other model developers) statements. How divers feel is one of their most important tools and the number of divers doing decompression and the ease of communication (the internet) has been a major driving factor.

Not feeling "as well" after a dive is thought to be one of the first signs that decompression wasn't as good as it could have been. Models are being tweaked based on how divers feel and we modify the way we handle decompression based on how we feel.

DAN and the recreational agencies are just now making a big deal about deep stops but technical divers have been using them and have known they work for a long time. It's about time they catch up. LOL'

The use of higher FO2 gas in one stage of the dive or another is an important part of all this.

PADI still claims that it doesn't help recreational divers but their about the only ones and I think it's because they don't want to develop new tables. LOL

If you're not equiped or trained to switch gasses on the way up it's best to have less nitrogen in the one gas that you have and stop (safety stop if you wish) deeper.

Avoid manufacturers or agencies that try to make this harder or more expensive than it needs to be.

 

[Scubaguy62]

Rick,
Nitrox compatibility has nothing to do with the ability to switch back and forth between standard air and nitrox. It simply means that the materials of the reg do not deteriorate due to the higher O2 percentage.

I agree with you Ron. What I was saying, though, is that Mares' standard regulators are claimed by the manufacturer to not be safe for use with nitrox, when in fact they are.

I just called my buddy with a Mares Surveyor Nitrox and he confirmed that the manual has a warning that when switching from air to nitrox the device needs to be O2 cleaned.

What device needs to be O2 clean? The Mares Surveyor Nitrox is non AI dive computer. I dive with an Aeris Atmos 2, and if I switch from nitrox to air, the gas mode will not set to "air," but will set from say 32% to 21%. Does the Surveyor Nitrox computer tells the diver to have the reg O2 clean if switching from nitrox to air? Mares computers are notorious for being overly conservative, so if it does, I'm not surprised.

I seriously doubt that Mares puts that warning in the manual to get you to buy another reg. It would give them a strong competitive disadvantage. I would be suspicious that the reg contains materials that deteriorate in higher O2 environments. I would ask the tech next time your reg serviced.

I bought my regs new about 3 years ago and that is the warning that came in the box, because at the time Mares actively promoted their Nitrox regulator, which was to be used only on mixes of up to 40%. So, in a manner of speaking, it wasn't their primary purpose at the time, but it was their bottom line. Their obvious primary purpose was to disclaim liability for any failure that may occur if the reg was used with nitrox, which leaves only two options, either purchase a Mares O2 kit for your reg (which is unreasonably expensive), or purchase a Mares Nitrox reg (which is also unreasonably expensive. Come to think about it, I have not seen the Mares Nitrox reg being advertised that much anymore, so I wonder if they still make them. If they don't, I wonder why!

Rick