Maximum Operating Depth (M.O.D.) S.C.U.B.A. Diving On Air.

[boulderjohn]

Some will talk about narcosis, but those are usually dated courses since our current understanding is that oxygen and nitrogen are comparably narcotic so there is no narcosis benefits from diving nitrox.

Maybe.

Objective vs. Subjective Evaluation of Cognitive Performance During 0.4-MPa Dives Breathing Air or Nitrox - PubMed

 

[Boston Breakwater]

I'm a little surprised that someone who, according to their profile, is EAN certified and an instructor says this.

I'd expect someone with credentials like that to be able to calculate MOD for any standard mix like EAN36, EAN32 and EAN28. Whether it's for 2 bar, 1.6 bar, 1.4 bar or any other pPO2. By extension, I'd expect that person to be able to calculate the MOD for any oxygen percentage, like 34% or 21%.

In other words, I'd expect someone who is EAN certified to be able to calculate the MOD for EAN21 at 1.4 bar O2. Perhaps even be able to reflect on the differences between air and EAN21. Me, I dive both nitrox and air. My PDC is permanently in nitrox mode, and if my tank contains air, I'll just tell my computer that I'm diving EAN21. Not unexpectedly, it gives me the same NDL times as if I told it I was diving air. It doesn't give me the MOD, though, because it doesn't have that functionality in air mode.

Hello. Sometimes, people cannot read between the lines. It's purpose was to engage thought, and I have seen some extremely good answers.
Your reply......I'm a little surprised that someone who, according to their profile, is EAN certified and an instructor says this.

I'd expect someone with credentials like that to be able to calculate MOD for any standard mix like EAN36, EAN32 and EAN28. Whether it's for 2 bar, 1.6 bar, 1.4 bar or any other pPO2. By extension, I'd expect that person to be able to calculate the MOD for any oxygen percentage, like 34% or 21%.

In other words, I'd expect someone who is EAN certified to be able to calculate the MOD for EAN21 at 1.4 bar O2. Perhaps even be able to reflect on the differences between air and EAN21. Me, I dive both nitrox and air. My PDC is permanently in nitrox mode, and if my tank contains air, I'll just tell my computer that I'm diving EAN21. Not unexpectedly, it gives me the same NDL times as if I told it I was diving air. It doesn't give me the MOD, though, because it doesn't have that functionality in air mode.
My apologies for not living up to your expectations.....
air vs Ean21 and tanks
Nitrox at Utah Dive Shops
Diving Calculators
Please, reflect the difference between "Air." and EANx21......Thanks.
Cheers.

 

[Storker]

Sometimes, people cannot read between the lines.

Well, some of us prefer to relate to what is said or written, rather than guessing what might or might not be found between the lines. If you want to say something, say it. If you want to ask for something, ask. It makes life a lot easier for everybody.

Please, reflect the difference between "Air." and EANx21......Thanks.

That's simple. For all practical purposes, it's zero. If by "Air" you mean air - without the scare quotes.

 

[Boston Breakwater]

Well, some of us prefer to relate to what is said or written, rather than guessing what might or might not be found between the lines. If you want to say something, say it. If you want to ask for something, ask. It makes life a lot easier for everybody.
That's simple. For all practical purposes, it's zero. If by "Air" you mean air - without the scare quotes.

Hello. I'm a little perplexed, as to why? You couldn't answer the questions? Please, refer to the O.P. At least, your maximum depth could have been shared.
Your quote........"Perhaps even be able to reflect on the differences between air and EAN21." in your reply. And then, as a retort you say " That's simple. For all practical purposes, it's zero. If by "Air" you mean air - without the scare quotes."
Sooooo, Your'e saying there is no difference between "Air." and "EANx21" Please, enlighten me.
Cheers.

 

[Storker]

Sooooo, Your'e saying there is no difference between "Air." and "EANx21" Please, enlighten me

I'm going to answer as if your question is serious.

Dry air consists of 20.95% O2, 78.08% N2, 0.93% Ar, 0.033% CO2 and 0.007% other gases.

EAN21 (Enriched Air Nitrox 21) is obtained by adding enough O2 to air to reach an oxygen content of 21%. Note that the "21" is given by two significant digits, so in practice it covers any oxygen content between 20.5% and 21.499999...% For argument's sake, I'll impose a higher precision and say I want 21.00% O2.

So, I add a very, very small amount of O2 to my tank, reaching exactly 21.00% O2. I have no idea about how I can do that in practice since my analyzer has a margin of plusminus 0.1% at its best, but I can always do the theoretical exercise. Now, my tank of EAN21 contains 21.00% O2, 78.03% N2, 0.93% Ar, 0.033% CO2 and 0.007% other gases.

So, air vs EAN 21.00:
O2: 20.95% vs 21.00%, difference: 0.05 percentage points
N2: 78.08% vs 78.03%, difference: 0.05 percentage points
Other gases: same content within two decimals.

Now, let's reflect on the fact that a normal O2 analyzer can't give better than 0.1% precision, and we understand that there is no measurable difference between air and EAN21. Unless we take our gas to a precision lab with quite advanced instruments, of course.

I can't measure any difference. My MOD isn't significantly changed, neither is my END. IOW, for all practical purposes there is no difference between filtered, dry air and EAN21. And unfiltered, moist air should not be filled on a scuba tank.

 

[Boston Breakwater]

I'm going to answer as if your question is serious.

Dry air consists of 20.95% O2, 78.08% N2, 0.93% Ar, 0.033% CO2 and 0.007% other gases.

EAN21 (Enriched Air Nitrox 21) is obtained by adding enough O2 to air to reach an oxygen content of 21%. Note that the "21" is given by two significant digits, so in practice it covers any oxygen content between 20.5% and 21.499999...% For argument's sake, I'll impose a higher precision and say I want 21.00% O2.

So, I add a very, very small amount of O2 to my tank, reaching exactly 21.00% O2. I have no idea about how I can do that in practice since my analyzer has a margin of plusminus 0.1% at its best, but I can always do the theoretical exercise. Now, my tank of EAN21 contains 21.00% O2, 78.03% N2, 0.93% Ar, 0.033% CO2 and 0.007% other gases.

So, air vs EAN 21.00:
O2: 20.95% vs 21.00%, difference: 0.05 percentage points
N2: 78.08% vs 78.03%, difference: 0.05 percentage points
Other gases: same content within two decimals.

Now, let's reflect on the fact that a normal O2 analyzer can't give better than 0.1% precision, and we understand that there is no measurable difference between air and EAN21. Unless we take our gas to a precision lab with quite advanced instruments, of course.

I can't measure any difference. My MOD isn't significantly changed, neither is my END. IOW, for all practical purposes there is no difference between filtered, dry air and EAN21. And unfiltered, moist air should not be filled on a scuba tank.

I agree. The difference is negligible...Thanks.
Cheers.