Nitrox: Should I be worried?

[diverrex]

If divers are concerned about o2 content of tanks they are told have nitrox, why aren't they equally concerned about tanks that they are told have air? If mistakes can be made with nitrox fills, why can't similar mistakes be made with tanks that are "supposed" to contain air.
Makes sense to analyze all tanks if one is concerned about exceeding mod's.
Makes no sense to say, "I dive air so I don't need to analyze my tank.

That’s an interesting thought. I could see at shops that fill both air and Nitrox someone messing up.

 

[Searcaigh]

It's pretty straightforward really.

Analyse the tanks before you dive and if you're unable to, then don't use the tanks.

I for the most part dive nitrox all the time to manage my NDLs for my local diving. Fortunately I own my tanks, so as well as analysing and labelling at my LDS, I double check when I get home.

Diving overseas in SE Asia, all the dive ops I've used do a check on the tanks with you and label them accordingly plus sign a log and I wouldn't have it any other way.

 

[lionfish-eater]

Loading dock on an ordinary day at a large fill station

 

[drrich2]

am I being unreasonably paranoid?

No, but don't assume you won't be able to test your mix; give your dive op. the benefit of the doubt and ask about it. I've seen a range of practices; on my live-aboard trips there was always a log and divers were expected to not just personally analyze their tanks, but log the results, %02 and MOD. And I've been on a day boat where the subject wasn't brought up. In situations where most trust the stated tank mixes, the boat might not automatically get the analyzer out and announce it.

On Scuba Board, a few years back it seemed there was a powerful domineering sentiment that you must personally analyze every single nitrox tank you ever dive. The only possible exceptions were when you watched the dive op. employee analyze your tank in your presence and the tank didn't exit your custody, or you had an immediate blood relative (e.g.: spouse) with a strong relationship whose judgment you trusted (didn't get the sense that was considered on par with testing it yourself).

In more recent times, when the subject comes up, there's still a pretty strong 'pro-testing' sentiment (understandable, you may read anecdotes supporting it), but it doesn't seem quite as severe, and most divers still don't test for CO. People dive tank after tank of air untested, but balk at untested nitrox tanks.

I wish we had a reliable estimate of the real world risk of a 'bad tank' where the O2 mix (or CO contamination) would be off enough to jeopardize health.

Richard.

 

[Searcaigh]

most divers still don't test for CO2

CO2 ??

I think you mean CO

 

[drrich2]

Thanks, Searcaigh. Glad you pointed it out while I still had time to edit and fix it to avoid confusion, but error admitted.

Richard.

 

[twistypencil]

People dive tank after tank of air tested, but balk at untested nitrox tanks.

I think you mean, "People dive tank after tank of air *untested*, but balk at untested nitrox tanks" ?

 

[CT-Rich]

You should just ask to check. When I was in GC each diver had to initial the book and write the mix down. We just watched as they did it and read the meter. I saw them check the reference tank.

If they make a thing about i, dive air and don’t use them again.

 

[RayfromTX]

Test every tank. You will find mistakes and you will find tanks with elevated and unacceptable levels of carbon monoxide. On a liveaboard last spring I tested all the tanks on board after one of ours tested at 10 ppm. Out of about 100 tanks on board we found about 15 with levels greater than 5ppm and two with levels that pegged the cootwo. At levels greater than 30ppm the cootwo simply starts flashing TOO HIGH and will not give a higher reading.

On our last trip to Cozumel we found that condition on one or two of the approximately 50 tanks that we tested. I can't remember but is seems like it was two. The high tanks are always right next to one that tests at 0 ppm. Nitrox levels vary also from what you have asked for. I don't set my computer until I test, not because I think a 1-2% difference is going to send me into OxTox or DCS but because I'm going to test every tank I breathe anyway and then I'm going to use the accurate number.

I'm also not going to trust my gear setup to the friendly guy on the boat. Eventually you will experience reasons to take responsibility for your setup. Might as well instill good habits early. At first it will seem like a lot to get done on the way to the site. That will become second nature and and will take less time and make you a more competent diver.

Enjoy your trip!

 

[kelemvor]

Who are you diving with. All ops that offer nitrox should (and I *think* most do) have an analyzer available on board the boat. You can ask them to show you how to use it or just watch them and see the reading.

This. Every time I've got nitrox in Mexico, the operator has provided an analyzer. I bring a cootwo because it also tests for CO therefore I don't use theirs but they still provide one.

You analyze on the boat while going out to the dive site. That way you don't have to waste time on the dock. I guess it could be a problem if you got a wildly off mix, but so far that's never happened to me.