POLL, Nitrox tank use and analyze

[ThomasScherrer]

I dont seek to justify anything, just let people reveal what they did in a secret poll.
that is all, you can allready see on the results a few did it.
leave them alone, they know what they did, and the risk.

 

[OldNSalty]

I've used a tank that I didn't check myself but my buddy was the one picking up the tanks. I figured if I can trust him below the water I should be able to trust him above it.

 

[ClayJar]

When my significant buddy and I are diving, we'll analyze the mixes jointly. One person with the analyzer calling out mixes, one person with the pressure gauge calling out pressures, each measurement witnessed by the other diver, and all data written on fresh and dated tape on each cylinder. As we're both parties to the analysis of the mixes, it doesn't matter which of us gets which cylinder, which is convenient if we get a bad O-ring or one of us skips a dive or two. We can choose which mix and fill pressure we want for each dive.

There *was* however one boat trip where one of our students brought a nitrox cylinder onboard without analyzing it, and the analyzer on the boat died an unexpected and inconvenient death. It would be gross negligence to allow a student to dive with an unknown mix, so I was asked if I would consent to diving it myself. I did... but...

My dive was going to be staying at the top of the structure, which is rather shallow. Knowing the depth, I then calculated what the limiting mix would be given that depth as the MOD (i.e. I used the "best mix" calculation we teach in all our nitrox classes). Knowing that mix, I could do some quick algebra to calculate the pressure of pure oxygen that would be required to arrive at a partial pressure blended fill of the richest acceptable mix for that depth. We would have to go well out of our way to intentionally and at some effort reach that rich a fill, and if we did, it would not have left without analysis and two signatures. So...

Did I analyze that mix using an oxygen analyzer? No. Did I analyze the mix using lots of logic and math to ensure that it would not cause *me* harm on *my* very shallow dive? Yep, I'd say I did. Would I ever dive a cylinder with a mix that hadn't been analyzed and that I had not been able to sufficiently vet through math and logic as being acceptable for that particular dive (which would have to be shallow enough or the confidence intervals are not high enough)? Certainly not!

In Bonaire, there was one guy we saw often while we were picking up more nitrox. Several times he asked us is we'd ever seen a too-rich fill from that shop. Each time we said, no, we hadn't, but that it'd be unconscionable to simply assume that the fact we'd never seen it means it can never happen, and analyzing only take a few minutes for each load of cylinders. Who knows, if you *do* get a too-rich mix, you may not regret it one iota. On the other hand, those you leave behind may think otherwise.

 

[diverrex]

One time we dived with a boat op that supplied the tanks. We had never dived with them before but knew a lot about them and their good reputation. We had ordered Nitrox tanks. When we boarded the Captain said the tanks were 32% and we could trust him. That was the only time I did trust someone and not test them myself. But I also knew we wouldn't be going below 90 feet and the profile would be within air NDL, so I figured the risk was minimal. The Nitrox was just extra safety margin. In fact we left our computers on an air setting. Stll not sure I would do that again.

 

[lowviz]

I am required to test anything (other than air) at my LDS and sign off in their book before they will let me remove it from the shop. The tanks will get tested again...

I own a trans-fill whip. For this reason alone, I test everything (Analox O2 E-II) a second time when I load the tanks into the car for the dives. Even air fills. Only takes a minute.

Anyone that pushes NDL limits really needs to be certain of what they are breathing.

 

[TMHeimer]

Can't vote. Don't own an analyzer. I observe what they do and watch them analyze, confirm the blend. Trust their equipment & analyzer. I would imagine many do this.

 

[50Fathom]

Rule Four: "Always analyze your gas".

I always do, even when breathing a known mix that I mixed myself. Shoot, I even analyze air. If for no other reason than to stay in practice and ingrain the habit.

 

[TSandM]

I voted that I always analyze, but there is an exception . . . From time to time, my husband picks up the tanks at the shop, and analyzes them. (All tanks are analyzed before removing them from the store.) If the tape has my husband's writing on it, I will dive the tank. If he decides he wants to get rid of me, there are easier ways

So, all tanks are analyzed, but I don't always do it myself.

 

[scubadobadoo]

I voted that I always analyze, but there is an exception . . . From time to time, my husband picks up the tanks at the shop, and analyzes them. (All tanks are analyzed before removing them from the store.) If the tape has my husband's writing on it, I will dive the tank. If he decides he wants to get rid of me, there are easier ways

So, all tanks are analyzed, but I don't always do it myself.

What she said. So, technically, yes I have also used a tank without checking it myself. That said, most of my dives are pretty shallow shore dives.

 

[mathauck0814]

#1 reason of diving accidents has got to be divers breathing the wrong gas. Failing to analyze your mix is an invitation for a demonstration of Darwinism.