Analyzing your own nitrox tanks

[Paula vollmer]

My

I took the PADI nitrox course this week, and it was made very clear that you always analyze your own tanks before using them. Then I was told that the analyzers are very expensive and there is usually one around to use.

The next day I got on the boat with the same shop (my instructor was on board). I used their analyzer and got a very different reading from what was marked on the tanks. A crew member came to help me and it turned out the analyzer was drifting after being calibrated. After we tried a few times and got varying readings approaching what the markings said, she told me that it was okay to use the percent marked on the tank.

That night I met a local guide for a dive and she provided the nitrox tanks. She didn't have an analyzer so I went with what she had marked on the tanks.

It seems like many of the "rules" I've been taught in scuba courses tend to be more "guidelines" when I get out in the real world. Is this one of them? What are people's practices as far as analyzing your own tanks?

 

[MrVegas]

In the U.S., every dive operator I have gone out with when diving Nitrox has required a signature after either witnessing a test or making me do it myself. In the U.S., a shop has always at least had an analyzer available and asked me if I wanted to test the tanks (and never given me hard time if I say "yes"). On a recent trip in the Caribbean, it seemed like all tanks with painted green tops were 32% and all tanks with painted blue tops were air, and nobody analyzed anything. I dove the nitrox tanks, but I think I'm buying an analyzer for the next trip there. (Diving was good, though!)

 

[Allen-1]

In the U.S., every dive operator I have gone out with when diving Nitrox has required a signature after either witnessing a test or making me do it myself. In the U.S., a shop has always at least had an analyzer available and asked me if I wanted to test the tanks (and never given me hard time if I say "yes"). On a recent trip in the Caribbean, it seemed like all tanks with painted green tops were 32% and all tanks with painted blue tops were air, and nobody analyzed anything. I dove the nitrox tanks, but I think I'm buying an analyzer for the next trip there. (Diving was good, though!)

Somewhat similar experience. Diving in Florida, tanks were analyzed in front of me, and I signed their log book.

In Roatan, I had two slightly different experiences. One operation analyzed in front of me, the other made an analyzer and logbook available.

I was taught to check mixture and pressure of any tank I'm using and that practice makes sense to me, so I do so.

I bring my NuVair quickstick with me any time I dive; if the shop doesn't have an analyzer - it's not a problem.

 

[OMyMyOHellYes]

The venues I have dived all had a shop analyzer for divers' use. I will use theirs, but I carry my own and validate the shop's prior to first use. After that I usually rely on the shop's analyzer so I don't have to carry mine.

 

[Norwegian Cave Diver]

There should be a dedicated tank of 20.9% for you to calibrate the O2 sensor to. Then analyze your dive tanks.

 

[San Diego Climber]

There should be a dedicated tank of 20.9% for you to calibrate the O2 sensor to. Then analyze your dive tanks.

the whole world has that tank, apparently it's 1.8 x 10²³ ft³ and filled to ~14.5 PSI / 1 ATA (Google: what's the volume of earth's atmosphere in cuft )

 

[BRT]

There should be a dedicated tank of 20.9% for you to calibrate the O2 sensor to. Then analyze your dive tanks.

I always use the big tank for calibration. In all seriousness, if you try to calibrate right after trying to analyze a nitrox tank it will not work correctly.

 

[Norwegian Cave Diver]

Both of you are missing the point.
If the shop has a dedicated tank that is kept where the analyzers are hanging on the wall - marked with 20.9% - then that tank can be trusted to be air and only air. It eliminates the opportunity for it to be a tank that has any blend other than air in it.

 

[LFMarm]

I honestly think that not analyzing every tank you use, including air, for O2 and CO is a significant risk. The cost in dollars and time is low compared to everything else involved in diving. If you dive with reputable operators with good SOPs and well maintained equipment, you are very likely to be safe regardless of analyzing but the consequences of one bad fill are so high that I don’t think it’s worth the risk.

 

[LFMarm]

Both of you are missing the point.
If the shop has a dedicated tank that is kept where the analyzers are hanging on the wall - marked with 20.9% - then that tank can be trusted to be air and only air. It eliminates the opportunity for it to be a tank that has any blend other than air in it.

It may still have CO in it. Why not test for both. It only takes 20s more.