nitrox or air,

[BoltSnap]

Always nitrox if available with the maximum O2% appropriate for the depth (<=40%).

 

[Kairoos]

A nitrox fill costs $4/tank at my LDS and an air fill costs $3/tank. Regardless of tank capacity so I always dive nitrox.

If I wasn't diving my own tanks and the price difference was $10 a tank or something I'd probably dive air unless the depth of frequency of dives called for nitrox.

 

[Lorenzoid]

No reason not to dive Nitrox (EANx) if an appropriate mix (percentage) is available. Keep in mind that while we often think of Nitrox in terms of the more or less standard mixes, like 28%, 32% and 36%, anything between 21% and 40% falls within the definition of ("recreational") Nitrox. There's not a whole lot of difference between air (21%) and EAN28.

For a week of "a lot of diving," I'm not sure I would be too concerned. Even on a liveaboard, 4 dives a day using, say, 32% probably wouldn't be an issue. But maybe I would be more concerned on a 10-day liveaboard. Or if I were using 36% or other relatively rich mix. If I was doing a lot of diving over the course of a 10-day liveaboard or a lot of diving on 36% might I take a break at some point to reduce my oxygen load?--maybe. But by "break" I'm not sure I mean I would dive on air--rather, I think I would just sit out a dive or two.

For further reading, there are a number of threads you can search for where CNS oxygen toxicity, etc., has been discussed in the context of recreational diving. There seems to be some debate as to whether we recreational divers doing a lot of diving over the course of week or so need to be concerned or not.

 

[tursiops]

No reason not to dive Nitrox (EANx) if an appropriate mix (percentage) is available. Keep in mind that while we often think of Nitrox in terms of the more or less standard mixes, like 28%, 32% and 36%, anything between 21% and 40% falls within the definition of ("recreational") Nitrox. There's not a whole lot of difference between air (21%) and EAN28.

For a week of "a lot of diving," I'm not sure I would be too concerned. Even on a liveaboard, 4 dives a day using, say, 32% probably wouldn't be an issue. But maybe I would be more concerned on a 10-day liveaboard. Or if I were using 36% or other relatively rich mix. If I was doing a lot of diving over the course of a 10-day liveaboard or a lot of diving on 36% might I take a break at some point to reduce my oxygen load?--maybe. But by "break" I'm not sure I mean I would dive on air--rather, I think I would just sit out a dive or two.

For further reading, there are a number of threads you can search for where CNS oxygen toxicity, etc., has been discussed in the context of recreational diving. There seems to be some debate as to whether we recreational divers doing a lot of diving over the course of week or so need to be concerned or not.

I'd be surprised if you can get anything other than 30-32 on most recreational liveaboards....I think they all use membranes now, so get only one mix out.

 

[Lorenzoid]

I'd be surprised if you can get anything other than 30-32 on most recreational liveaboards....I think they all use membranes now, so get only one mix out.

I'm sure you're right. I was just trying to point out that there might be some conceivable circumstance where one is doing "a lot of diving" over the course of a week or so in which they might want to take a break--though perhaps not just switching to air as the OP asks. No, I think the real-world answer is as others have said: no reason not to dive Nitrox all week.

 

[Bob DBF]

For a multi-day trip with multiple dives per day, I use Nitrox if it is available at a reasonable price.

Locally Nitrox is an hour drive in the wrong direction and pricy, so I dive air.


Bob

 

[mike_bayer]

Unless you are doing decompression diving you will not likely come close to CNS O2 limits.

Since most divers tend to dive in multilevel profiles and don't spend the entire dive at the maximum PO2, the actual oxygen clock rarely reaches 20 percent of the dose limit.

From the IANTD CNS Repetitive Chart, if you have hit 100% on your CNS O2 clock, a 30 minute surface interval will put you at 83%, a 90 minute SI will put you at 49%, and 6 hours will drop you to 7%.

Also between the last dive of the day and the first of the next day is usually at least 12 hours which leave 8 halftimes for oxygen, so even at 100% exposure your clock is theoretically reset.

The hazards of CNS oxygen toxicity are easily avoided by ensuring that your dive profiles don't violate the NOAA limits. Set your PO2 at 1.4 (less for longer dives), watch your computer's display of dose accumulation, and do not exceed the maximum depth limit for your nitrox mix.

Oxygen Partial Pressure (PO2) in ATA, Maximum Duration for Single Exposure in Minutes, Maximum Total Duration/24 Hr. Day in Minutes
1.6 45 150
1.5 120 180
1.4 150 180
1.3 180 210
1.2 210 240
1.1 240 270
1.0 300 300

 

[redacted]

I use nitrox when it is free or when it gives me more bottom time. Otherwise, I am fine with air.

 

[dmaziuk]

Disclaimer: IANA Biomedic, I just work for them.

Two of several theories of disease and aging are the bad old free radicals and the new kid mitohormesis. The first says all free radicals are to be eliminated, antioxidants are good, the oxidant: oxygen is bad bad bad. The new one says oxidative stress is good for you -- in small doses -- and breathing extra oxygen should make your cells more resistant to the badness of free radicals.

Seeing as the scientists can't get their oxygen story straight, I am staying off extra O2 until I have a pressing need for it. When I start getting limited by my NDL, I'll worry about going nitrox. Until then it's air for me.

 

[Steve_C]

the oxidant: oxygen is bad bad bad..

I will note that I have survived over 70 years of breathing 20% (and sometimes higher O2). Only noticable problems have been at higher elevations where I had less of it.