Do you think Nitrox is a deep diving gas?

[Rainer]

You still have to off-gas the He. There's no (appreciable) deco advantage to using He to replace N2. He is used to reduce narcosis, not to reduce decompression obligations.

webdivecc: by Helium "extending NDLs" - of course I mean that by lowering our nitrogen intake by adding helium to the mix, we are lessening our exposure to N2 and thefore extending our "no decompression limits" - a term which is, I appreciate, not relevant to technical diving, however one that more people would understand.

 

[dschonbrun]

I agree with Rainer.

First, Air used for diving is a form of Nitrox if one wishes to be picky... and many people dive air to over 40m. The original topic is a bit of a trick question depending on level of knowledge, and frankly it is ambiguous at best.

To a recreational diver with PADI or SSI, YMCA... "Deep" typically means 30-40m.
To an advanced diver working with normoxic trimix... "Deep" may mean 55-70m.

Ambiguous questions always generate a wide range of answers.

 

[MarkHerm]

To answer this question, I think it is important to define the used terms cautiously and to use some kind of benchmark to define what the term "deep" actually refers to.

Nitrox in recreational diving is defined as a gas blend that contains more oxygen than it is found in normal air ( > 21%).
For the average recreational diver the alternative to nitrox is air. When compared to air, nitrox contains a higher level of oxygen. Because oxygen is getting toxic at depth you cannot dive as deep as a diver who uses air. Now the answer to the question is simple: When compared to air, nitrox is definitely not a deep diving gas.

 

[HowardE]

The OP was specific to state Mixes > 21% - This kind of rules out Hypoxic mixes.

Also - he's not talking about Air, but ENRICHED AIR NITROX.

 

[halocline]

If the Maximum Operating (or Oxygen) Depth of a gas is based on its partial pressure (absolute) then how can diving at altitude NOT affect the MOD of a particular blend?

The problem is that Don's instructor was under the impression that the altitude decreased the MOD for a specific blend, just like altitude affects NDLs. Don challenged this, essentially saying that "no, I don't have to dive shallower on this nitrox blend because of the altitude." Don was right in that assertion.

While you are correct in saying that altitude very slightly increases the MOD (I guess that's what you're saying) your statement gave me the impression that you were agreeing with his instructor, until I read your math a few times.

The point is that altitude does not decrease MOD for a specific nitrox blend, nor does altitude affect nitrox MOD to anywhere near the extent that it affects N2 gradients on surfacing.

 

[Crowley]

hi mattboy - thanks for the clarification. I did consider this in my original reply but since we are picking nits (please note I have my tongue firmly planted in my cheek now!) then no, I don't agree with Don's instructor (sorry to talk about you in the third person, dude!) but nor did I agree with the statement that "altitude would not affect the MOD".

So now lets all be friends and have a beer together and talk about something else!

Cheers all,

Crowley

 

[CompuDude]

To answer this question, I think it is important to define the used terms cautiously and to use some kind of benchmark to define what the term "deep" actually refers to.

Nitrox in recreational diving is defined as a gas blend that contains more oxygen than it is found in normal air ( > 21%).
For the average recreational diver the alternative to nitrox is air. When compared to air, nitrox contains a higher level of oxygen. Because oxygen is getting toxic at depth you cannot dive as deep as a diver who uses air. Now the answer to the question is simple: When compared to air, nitrox is definitely not a deep diving gas.

See posts 123-129, above, to see where you're wrong in this statement.

To summarize, however, 28% Nitrox (EAN28) has an MOD right at the recreational limits, therefore you CAN dive as deep (albeit still within the recreational limits under discussion) as a diver using air. Longer, too. So by your definition of Nitrox (>21%), Nitrox can be a deep diving gas... as long as the MOD of the mix chosen is appropriate to the max depth of the dive (and the dive is restricted to recreational depth limits).

It is a mistake to assume Nitrox begins at 32% and goes up from there.

 

[martin_taz36]

I sue nitrox for repetitive diving when leading dives, so that I don’t have such big nitrogen builds up. Especially if you are leading repetitive dives every day.

 

[Rainer]

I sued nitrox for repetitive diving when leading dives, much better

What did you settle for? Hope you took him to the cleaners.

 

[Reg Braithwaite]

There are no good arguments for NOT using Nitrox.

There may be no good arguments for not using Nitrox responsibly, i.e. planning safe dives and diving the plan safely, however it does does place limits on what a diver can do safely.

As described in Lessons Learned, I was recently on a dive where another diver made an unannounced/unplanned/undiscussed descent to 130'. I was diving EAN32, which left me the chocie between aborting and diving below my MOD. Had I been diving air, I could have descended with him and persuaded him to retun to a moderate depth.

Nitrox is a trade-off. I personally take the benefits over the loss of flexibility in cases like this, however I would also accept as reasonable someone who wanted the flexibility. For example, a DM or instructor may routinely have to chase students back up to the planned depth.