Nitrox for shallow water artifact diving??

[Divin'Papaw]

@JimBlay,

Does it matter to you how your Nitrox is made--you know, whether it is made by blending air and 100% oxygen (continuous blending or not), or, alternately, by removing nitrogen from air?

rx7diver

No, not to me. With respect to diving it, all that is relevant is the relative percentage of N and O2. Doesn't matter how it is made.

Personally, I don't keep my tanks O2 cleaned so partial pressure blending is out. The shops I use bank Nitrox. I have no clue if they use continuous blending or a membrane system. I've never asked.

 

[rx7diver]

No, not to me. With respect to diving it, all that is relevant is the relative percentage of N and O2. Doesn't matter how it is made.

Personally, I don't keep my tanks O2 cleaned so partial pressure blending is out. The shops I use bank Nitrox. I have no clue if they use continuous blending or a membrane system. I've never asked.

So, you're not concerned about Argon or the other trace gases (Carbon Dioxide, Methane, Nitrogen Oxides, Ozone, etc.)?

rx7diver

 

[Divin'Papaw]

So, you're not concerned about Argon or the other trace gases (Carbon Dioxide, Methane, Nitrous Oxides, Ozone, etc.)?

rx7diver

I didn't say that.

 

[Wibble]

So, you're not concerned about Argon or the other trace gases (Carbon Dioxide, Methane, Nitrogen Oxides, Ozone, etc.)?

These are trace amounts compared with 79% nitrogen (or 68% nitrogen if on 32%).

 

[rx7diver]

I didn't say that.

Thanks, @JimBlay. Honestly, I had never thought about this (i.e., the fraction of Argon and other trace gases in EANx), until relatively recently, after reading something, somewhere, that it might be a concern. It was not discussed in my Nitrox cert course (c. 1993), nor in my Technical Nitrox cert course a couple of years later. This thread got me wondering again about this.

The fact is, the dose of Argon and these other trace gases a Nitrox diver is subjected to differs depending on how his/her Nitrox is made. I wonder if these differences contribute to why some Nitrox divers feel less fatigued after a Nitrox dive than other Nitrox divers. Admittedly, these doses are tiny (i.e., small partial pressures at recreational depths and exposures), but still ...

Anyway, something to think about!

rx7diver

 

[kelemvor]

The fact is, the dose of Argon and these other trace gases a Nitrox diver is subjected to differs depending on how his/her Nitrox is made. I wonder if these differences contribute to why some Nitrox divers feel less fatigued after a Nitrox dive than other Nitrox divers. Admittedly, these doses are tiny (i.e., small partial pressures at recreational depths and exposures), but still ...

Anyway, something to think about!

rx7diver

Yes, they differ in resulting trace gasses. I'm not sure at what point the trace gasses become a concern for divers.

 

[Divin'Papaw]

Thanks, @JimBlay. Honestly, I had never thought about this (i.e., the fraction of Argon and other trace gases in EANx), until relatively recently, after reading something, somewhere, that it might be a concern. It was not discussed in my Nitrox cert course (c. 1993), nor in my Technical Nitrox cert course a couple of years later. This thread got me wondering again about this.

The fact is, the dose of Argon and these other trace gases a Nitrox diver is subjected to differs depending on how his/her Nitrox is made. I wonder if these differences contribute to why some Nitrox divers feel less fatigued after a Nitrox dive than other Nitrox divers. Admittedly, these doses are tiny (i.e., small partial pressures at recreational depths and exposures), but still ...

Anyway, something to think about!

rx7diver

I was taught that they are so small that we combine them with the percentage of N and consider that all to be N. I was just recently re-reading Mark Powell's Deco for Divers and he mentions exactly this. That is why we treat air as being 79% N when it is actually 78% and change with the trace elements making up the difference. Oxygen is 20.9% and change.

With Nitrox I always follow that same logic. After all that is what our dive computer's assume as well. Unless you're using Helium as well, anything other than the Oxygen is assumed to be Nitrogen.

Now the possible presence of dangerous trace elements is a different matter. That gets to the question of gas quality. I use two reputable shops for all of my fills. That is good enough for me. Others test their fills for CO. That is a whole different dead horse that has been beaten many times.

 

[Storker]

Me feeling better and less tired after a dive is not considered fatigue by the studies definition although it is by mine.

If i really want to hit my bunk before 8:00 pm after two deep (ish) dives, is that clinical fatigue? If I want to roll down my car window while driving home from a two-tank outing to avoid falling asleep, is that clinical fatigue?

If I don't really want to hit my bunk before 8:00 pm after two deep (ish) dives on nitrox or don't want to roll down my car window while driving home from a two-tank outing on nitrox, is that irrelevant? Scientifically speaking, you can't regard those datapoints because they haven't been obtained during a double-blinded study, but still...

 

[Storker]

So, you're not concerned about Argon or the other trace gases (Carbon Dioxide, Methane, Nitrogen Oxides, Ozone, etc.)?

rx7diver

In atmospheric air,
Ar is less than 1%
CO2 is a lot less than 1%
NOx is a lot less than 1%
CH4 is a lot less than 1%
O3 is a lot less than 1%

In rec diving, I'd worry a lot more about the part that makes up some 79% of atmospheric air and has proven to be both narcotic and central to DCS.

 

[rx7diver]

I was taught that ...

I think if I were a physiology (or exercise physiology) student looking for a research topic, I might propose to my advisor, committee, and IRB, a research study that looked at "post-dive fatigue", using "type of Nitrox" as its primary "treatment" (three levels: (a) Nitrox made with five-nines Oxygen and five-nines Nitrogen, (b) Nitrox made with five-nines Oxygen and air, and (c) Nitrox made by removing Nitrogen from air). Maybe incorporate repetitive dives, for a repeated measures experimental design.

Maybe write the grant proposal to either use the multi-place hyperbaric chamber at your AAU university, or do actual dives somewhere in the South Pacific.

Maybe this has already been done...

rx7diver