Systematic use of oxygen analyzers by advanced divers ? [Poll].

[KenGordon]

Agreed. In fact, I do not understand the motive for the OP's endless set of polls, nor do I think there is any generalizable conclusion one can make from the results.

They seem highly successful to me. Maybe Pete is paying him to drum up traffic

 

[tursiops]

They seem highly successful to me. Maybe Pete is paying him to drum up traffic

That's a better answer than the OP has given!

 

[TMHeimer]

This post is simply an explanation of what the danger would be if the tank believed to be air actually had nitrox.

The most obvious danger is oxygen toxicity, and that is certainly possible. Some of the most celebrated cases of oxygen toxicity were caused by exactly that. For example, we have the case of Carlos, mentioned earlier, who thought he had air but actually had pure oxygen, which he breathed at 100 feet for a while until he toxed. Another case is the diver in South Florida who thought he had air in his doubles, which he used at about 160 feet for about 20 minutes before he toxed. (I talked with his buddy.) It turned out he had 36%.

Notice, though, that both of those cases had elements that are out of the range of recreational experience. In one, the diver was breathing pure oxygen at 100 feet. In the other, the diver was at 160 feet for with 36%. Both of these dives fall into the realm of technical diving.

What if a recreational diver were breathing a more common recreational nitrox mix (32% or 36%) in an AL 80 and thought it was air? What are the chances that diver would suffer a toxic effect? The MOD for 36% is 90 feet at the 1.4 standard and 110 feet at the 1.6 standard, and you have to be at that depth for a fair (and unpredictable) amount of time before something happens. Those depths are beyond what most people dive, and if the diver believes he or she is on air and trying to stay within NDLs, they will not be at those depths for long.


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Yeah, that all makes sense to me. I should have figured through this reasoning long ago instead of just trusting that the well known shops I patronize would give me Air when I asked for it.
The objective of the Poll is unclear to me. I would be interested in how many who dive only Air actually use their own analyzer to check that it is Air. I'm pretty sure not many do.

Click "Expand" for my reply...did it again.

 

[martincohn]

If I breath it I check it. CO and O2 every tank. Its too easy to prevent that problem.

 

[Storker]

If I know that my tanks have been filled with air, I don't analyze. If I'm diving nitrox, or if there's a decent chance that at least one of my tanks is filled with nitrox, I always analyze. If the tank contains nitrox I analyze twice. With two different analyzers. I use the filling station's analyzer when filling to mark the tank, and my personal analyzer on-site when assembling my gear. And if the results differ by more than 1 percentage point, I call the dive.

 

[PfcAJ]

If I know that my tanks have been filled with air, I don't analyze. If I'm diving nitrox, or if there's a decent chance that at least one of my tanks is filled with nitrox, I always analyze. If the tank contains nitrox I analyze twice. With two different analyzers. I use the filling station's analyzer when filling to mark the tank, and my personal analyzer on-site when assembling my gear. And if the results differ by more than 1 percentage point, I call the dive.

So you dont analyze air tanks because you "know" they have air but you thumb the dive over a difference of a percentage point with two different analyzers?

Wacky.

 

[Storker]

So you dont analyze air tanks because you "know" they have air but you thumb the dive over a difference of a percentage point with two different analyzers?

Wacky.

If the filling station only provides air and I'm more than reasonably certain that I haven't mixed up the tanks (basically, if I'm using rental tanks), I operate as I did before I certified nitrox.

If the tank may contain nitrox, the two-analysers-one-percentage-point routine gives me an acceptable safety margin against a current-limited cell.

How is that wacky?

 

[PfcAJ]

Everyone should analyze their gas. Rental tanks can be filled with god-knows-what between the time they leave the shop and come back. Theres zero reason NOT to analyze.

1.5% = thumb the dive? Analyzers aren't that consistent day to day and brand to brand.

 

[kelemvor]

If the tank may contain nitrox, the two-analysers-one-percentage-point routine gives me an acceptable safety margin against a current-limited cell.

How is that wacky?

You can be reasonably certain your analyzer is working right if you use it correctly (calibrate frequently etc). The same can't be said for the shop's analyzer. With your method, you'll thumb a dive if the shops analyzer has a problem but yours does not. To me, that seems extremely cautious.

At the same time, you don't test tanks you suspect have 21% in them. To me, that seems caviler.

I think the fact that the two decisions seem to contradict each other may be why he described it as wacky.

 

[Storker]

You can be reasonably certain your analyzer is working right if you use it correctly (calibrate frequently etc).

No, I can't. Unless I test and/or change my analyzer's cell as often as RB pilots do, I run a realistic risk that my analyzer's cell is current limited. And I'm willing to bet a couple of beers that rec nitrox divers don't follow a such a strict procedure.

The same can't be said for the shop's analyzer. With your method, you'll thumb a dive if the shops analyzer has a problem but yours does not. To me, that seems extremely cautious.

I work with analyses in my day job. If I have only one data point, I have no way of knowing whether or not I should trust the numbers. If I have two independent data points which agree, I can be certain enough (for me) that I have the right number(s). If the two independent data points contradict each other, I have no way of knowing which is the right one (even if I might trust my own analyzer's data more). So, the prudent action would be to trust none of the data until I have a 3rd opinion.