Nitrox - practical limits?

[BlueDevil]

I am wondering what others see as the practical limit for using nitrox. It seems to me that light nitrox mixes, say around 28%, carry relatively little advantage over air so probably aren't cost effective.

There are a number of wrecks in my area in the 36 - 40 m range. For a 36m dive there is probably enough advantage in using a 30% mix for it to be worthwhile. But any deeper than that I am thinking it may not be worth bothering. For example, at 40m a 28% mix gives an EAD of around 36m, which seems like too little advantage to worry about.

What do you guys think is the practical limit of nitrox in terms of depth and/or O2 percentage? (Note: I am assuming MAX ppO2 of 1.4)

 

[String]

Generally >40m its not worth it. The deeper the less benefit from the max, especially if accepting a PPO2 of 1.4.

Nitrox is far more useful for 25-35m depth than anything else. Below that it gets less and less useful until the point theres no different to using air.

At the moment i keep 28% in my main 15l tank and 36% in my 12l.

The theory being the deepest dive is likely to be my first and unlikely to be below 40m and my second dive is usually under 30m.

Its not as useful as people make out.

 

[Randy43068]

take the class... read the nitrox book...

 

[String]

take the class... read the nitrox book...

What a totally useless and pointless reply to a sensible comment.

 

[Randy43068]

Yeah, I know.

 

[Randy43068]

OK, I'm sorry I smarted off. You're right, it is a good question.

 

[pickens_46929]

Every little bit of nitrogen I can avoid loading into my body is a good thing...

That said it's a practical matter... if it's only one dive... probably not worth while... if it's lots of dives over a weekend and nitrox is available (and cheap!)... no brainer... gimme gimme !!!

I generally figure that anything above 28% is worth looking into... 22-27% isn't worth while... but you never know... sometimes gas management comes into play here... might not even have enough time to really use the extra difference... with depth comes the need for more cu.ft. of gas...

 

[scubapolly]

If you only look at the bottom time of a single dive, you are right there isn't that much of a benifit. However that is not the only benifit of Nitrox. As pickens mentioned, it can make a big difference when you are doing multiple dives both increased bottom time and decreased surface interval. You also will find decreased fatigue. Occassionally I will even use nitrox in a pool session if it is late at night, or if I am tired before the class.

Polly

 

[Blackwood]

You also will find decreased fatigue.

I've personally not noticed that.

I will generally get a hot mix (I have 37 in my 100cf right now) and top it off with air for subsequent dives.

 

[JeffG]

Every little bit of nitrogen I can avoid loading into my body is a good thing...

Then a better choice would be 21/35 for the 36 - 40 m range. But then thats a bit beyond nitrox.