Diving shallow on Nitrox.

[KenGordon]

More nitrogen is more nitrogen. More nitrogen is more risk.

While you may not actually reach the NDL on a long 20ft dive you are adding nitrogen to those tissues. If you happen to be at the more sensitive end for DCS (eg an undiagnosed PFO) then your risk of injury is higher on air. If your profile is aggressive, for example multiple ascents while training, or your post dive activities are strenuous, for example moving kit a long way, up ladders or up a hill, then your risk increases.

Nitrogen saturation is a depth and time thing. Long exposures carry more risk, deeper exposures more risk.

DCS is a risk game, nitrox is a mitigation of some risk.

Focus of NDL as a measure of risk is rather indirect.

Why would a shallow site do nitrox fills? Maybe you do training the, then fill cylinders and go off to do proper diving somewhere deeper.

 

[Storker]

I usually have my cylinders filled after a dive, not before, then I store them full.

Me, too. And since I generally don't go deeper than 30m (~100' for any Metric-impaired readers out there) and have access to really cheap nitrox, my standard fill at home is EAN32. That's what I'll be using regardless of whether my dive is to 6m or to 30m.

If I know that there's a risk that I might end up deeper than 30m (which doesn't happen very often), I'll probably use either EAN28 or EAN23 (23% is roughly what I get if I take my tank with about 50bar EAN32 left and top it up with air).

 

[RainPilot]

I keep all my tanks filled with 32%. For recreational diving it keeps me good to 40m and I never have to fiddle with PDC settings etc etc. Cost difference at my LDS is not major, they keep 32 banked so its 3$ for an air fill and 5$ for 32%.

For me its convenient, I suspect that if one is doing multiple dives in shallow sites for several days, there would be a gain in your NDL from using EANx. Hell, if you used 80% O2 then you would be off gassing at 20 feet. If i was flying home and wanted to get a dive in before I left, I would easily take EAN80 for a last dive at 20 feet.

Obviously one needs to keep an eye on the CNS clock but there are some reasons to use enriched air for shallow dives, YMMV

 

[seeker242]

Don't you find the extra cost for 32% a concern when Air is just as good at 20'?

Not really. It's only $2.30 extra. That's worth the convince and simplicity.

 

[halocline]

Cost difference at my LDS is not major, they keep 32 banked so its 3$ for an air fill and 5$ for 32%.

If i was flying home and wanted to get a dive in before I left, I would easily take EAN80 for a last dive at 20 feet.

If I could get 32 for $5/tank I'd probably use it all the time as well. Here its $8 for air and $15 for nitrox.

I understand the logic of using O2 to accelerate off-gassing nitrogen, but I don't think that authorities like DAN would never condone shortening the time to fly based on O2-rich mixes. There's not enough data to quantify the risk reduction.

 

[sheeper]

i only dive nitrox.
when i'm doing a shallow shore dive or with students on our 20' shallow stuff i will often dive 40%. And i feel GREAT after the dive.

 

[Lorenzoid]

i only dive nitrox.
when i'm doing a shallow shore dive or with students on our 20' shallow stuff i will often dive 40%. And i feel GREAT after the dive.

Does Blue Heron Bridge Scuba offer Nitrox fills? I've rented air tanks there. Never even thought about asking for Nitrox for a 20 foot dive.

 

[sheeper]

Does Blue Heron Bridge Scuba offer Nitrox fills? I've rented air tanks there. Never even thought about asking for Nitrox for a 20 foot dive.

the shop there does indeed do nitrox fills!

 

[TMHeimer]

If I could get 32 for $5/tank I'd probably use it all the time as well. Here its $8 for air and $15 for nitrox.

I understand the logic of using O2 to accelerate off-gassing nitrogen, but I don't think that authorities like DAN would never condone shortening the time to fly based on O2-rich mixes. There's not enough data to quantify the risk reduction.

Those are the usual costs I have found both at our shop in NS and in the numerous places I've visited in the U.S.--almost double the cost of Air.

 

[Nikole]

There's no real benefit for using nitrox on a 20ft dive. But, who knows why people choose to do all sorts of things?

I think GUE (a technical dive agency) basically advocates the use of 32 nitrox for all recreational dives shallower than 110 feet. I'm not 100% sure about it, but I have heard that somewhere. I know that every cave and cavern dive I have done with GUE instructors has been with EAN32, and many of those dives were shallower than 40 ft. It's just something they do.

You'll find that nitrox is very helpful if you ever dive on a liveaboard where you are doing 4 dives/day to 60ft or deeper. It's the repetitive dives where it helps the most in terms of bottom time.

One of the guys that I dove with that 1 time with was a commercial diver and used the nitrox at 20feet...i didn't ask what his blend was. And my checkout dive was at rainbow river in Florida if you've been there u all know that is shallow. One of my instructors used nitrox in this dive. He believes in the placebo effect. I'm not advanced yet but I do want to try out nitrox just to practice with visually verifying the contents, filling out the log sheet, putting it in the computers... Etc...