Why Nitrox?

[Sharky1948]

I just checked back to my notes. It was stated that doing so was similar to reverse profile diving where the deepest dive is done last, which is not recommended.

I think you may be confusing two concepts here. A reverse profile typically refers to diving the shallowest part of an individual dive first. This is not recommended since it does result in poorer off-gassing (theoretically true and true based on statistical analysis.)

Recent evidence (DAN) indicates that there is no correlation between DCI and diving a shallow dive (with a good profile) followed by a deep dive (with a good profile.)

I suspect your instructor was assuming that you would do your deep dive first (and therefore using a lower ppO2 for CNS limit reasons) followed by a shallower dive with a higher ppO2 mix.

 

[HowardE]

When I took the NAUI NITROX course it was indicated that when doing repetitive dives within the same day that you could continue with the same O2 mixture or go to a richer mixture but you should never go to a leaner mixture.

Am I missing something or did I misread your posting?

You can dive whatever mix you want for whatever dive you're doing... Just plan your dive accordingly.

Switching to a leaner mixture is like going fro 36% to air... which is no problem, or diving 36% on the first dive then 32% on the second... also no problem

or diving 30% on the first dive, and then 40% on the second dive... no problem (given that the MOD's allow you to do plan those dives

 

[bdshort]

Being that I can fill up on air for free, I don't see a benefit for switching to a gas I'd have to pay for. As much as I've been diving, those costs would add up quickly.

Related question though. The slips of paper tha came with my tanks said that once the valves had been used for air, they could never be used for EANx mixtures. Why is this?

Brian

 

[dbombtek]

Im going to nitrox as soon as I can. I like the increased bottom times.

 

[rookers]

Related question though. The slips of paper tha came with my tanks said that once the valves had been used for air, they could never be used for EANx mixtures. Why is this?

This is only partially true. Once the valves (and any other components in the HP path) have been used with air that is not "Oxygen Compatible", they are not supposed to be used for gases other than air henceforth. This is because non 'oxygen compatible' air may have unacceptable levels of fuels/combustibles present that would contaminate the equipment.