How do you know you're diving 21% Nitrox?

[Colliam7]

If your diving a 21% mix ( Air ), how do you know it's 21%. Do you test your mix?

Interesting question. And, No, I do not test my mix when getting an air fill. I understand the response that a fill station isn't going to give nitrox away for free, therefore it is most likely that 'air is air'. But, 'to err is human', fill station operators are human (at least most of them appear to be) and I guess it is possible to fill a tank with nitrox if you get distracted, particulary if banked nitrox whips are positioned right next to the air whips. It is probably not a big issue, but it is also something I have not previously thought about. I have had the experience of getting a (presumed, after the fact) CO-contaminated tank, and that dive was not fun. So, now maybe I should finally get serious about an analyzer . . .

 

[Jim Lapenta]

If away from home I check. Otherwise, no because I either fill my own tanks or am there while the shop owner is filling them. None of the shops I use locally bank nitrox or have membrane compressors. Only one has a stick and it is still being hooked up (new owner). I do have all but my dbl 72's O2 clean for nitrox though.

 

[NJDiverMark]

Correct, but how do know it is 21% unless you test it.

if you tell a shop to fill a tank with air. unless you have a nitrox mix already in the tank, its gonna be air 21%. if there is any questions, test it!! theres no shame in doing so.

 

[DivemasterDennis]

Limiting this response, checkin air fills for nitrox content, I do not. At some level, one has to function on a little trust in those you do business with. (I do test for CO if source is other than my LDS). My LDS is where i get "local air" an I am one of the fillers. I know all their nitrox is in clearly labeled tanks, and have faith in their system of filling, storage and labeling. When on air on a dive boat, I assume that air is air, not some other mix. On liveaboards, I do the same, and when renting tanks from a shore concession, I also believe them as to air fills. So far so good. I read in this thread for the first time someone getting nitrox when they thought they had air. So far, Debbie and I have been safe. With a combined use of about 1700 air fills, I like our percentges.
DivemasterDennis

 

[fred3798]

My wife and I have been convinced. We will be buying a CO analyzer before our next dive trip. in the fall We'll keep using the O2 analyzers of the LDS/DM for Nitrox. Not sure I feel the need to test every tank of air for 21% but the logic is certainly there.

 

[MaxBottomtime]

I check my stage bottles to make sure they have either 50% or 100% in them, but my other tanks always have 21% in them. My LDS does not pump nitrox and I only use it for decompression.

 

[RJP]

If I'm gonna dive it, and I didn't fill it, I'm gonna test it. Takes 5 seconds, doesn't cost anything, no downside.

 

[mbs]

Fill my own tanks at home so no. Travelling and diving nitrox I only test the nitrox tanks. Have there been any documented cases of either an o2 hit because of or an unmarked tank mistakenly filled with >21%?

 

[beaverdivers]

Limiting this response, checkin air fills for nitrox content, I do not. At some level, one has to function on a little trust in those you do business with.

So why not trust their nitrox fills, don't bother testing and just go diving. Doesn't this violate the #1 Rule of diving nitrox? Isn't air nitrox? How do you know what you are breathing if you don't test it?

When on air on a dive boat, I assume that air is air, not some other mix. On liveaboards, I do the same, and when renting tanks from a shore concession, I also believe them as to air fills. DivemasterDennis

Never assume, always test your mix. Isn't that the protocal for diving nitrox?

 

[TomZ]

I check for CO, every tank. It takes about 30 seconds more to check for O2. Yes. I check all tanks for O2 level. I have the toys, why not use them?