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

[Storker]

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

Not my experience. I routinely get less than 1% difference from day to day, or between my club's analyzer and my personal analyzer. If I get 1.5% difference, something is wrong.

 

[Gareth J]

I always make it a point of principle to test my analyser against 100% O2, then air.

I would do a check at the start of the season, then periodically during the summer. Although I dive all year, generally during the winter I'm not using rich deco' mixes.
On the occasions I didn't have O2 available, at a push, I would use a rich deco, then check it measured 21% at air.
That gave me some assurance the cell hadn't degraded and was voltage limiting.

Normally we have more than two on a boat, most of us have our own anyway, so if there is any doubt we can do a comparison.

Gareth

 

[ChuckP]

If you're diving a wreck and working at 110', you're 32% nitrox tests 32 with one and 34 with another, you thumb the dive? I got two 36% (labeled) tanks one day instead of 32 and 36, oh wait, they tested 35.6 and 35.8, thumb the dive? Not.

Test the air around you, test the air in the air tank - are you testing for CO2?

IMHO - you're being way over analytical (there's a hidden word in there) for rec diving.

If you're doing two or three dives in one day, you run off with tanks you think are 32%, you get to the site and your widget says they are 30% - why not just alter your plans based on the lower % or even air for that matter? If they tested 34%, same thing, alter your plans... Plug a number into your tables or computer that makes you warm and fuzzy and enjoy - the fact that you over analyze an enriched mix but not basic air makes no sense.

 

[lowviz]

There is no magic here. You calibrate your O2 analyzer with reference gasses that either span or include your intended measurement. I use pure O2 and air. A single point calibration is exactly that, you are good for that concentration only.

EAN-32 vs EAN-36? It is a simple depth change on the tables.

FWIW, I don't bother to check if it doesn't matter...

 

[Gareth J]

If you're doing two or three dives in one day, you run off with tanks you think are 32%, you get to the site and your widget says they are 30% - why not just alter your plans based on the lower % or even air for that matter? If they tested 34%, same thing, alter your plans... Plug a number into your tables or computer that makes you warm and fuzzy and enjoy - the fact that you over analyze an enriched mix but not basic air makes no sense.

That used to be more or less what you where taught in the early days.
If the mix wasn't correct on checking them on the boat you recalculated.
If the mix was low,.You had a choice, recalculate the EAD (Equivalent air Depth) and replan the decompression, or if using a fixed table, use the next table, down. MOD was based on the actual analysed gas.

It's always better to be a little conservative with the MOD.

 

[JackD342]

I’m just not sure what you are trying to learn from this poll. Most divers on ScubaBoard are going to say they always test their gas. Period. But that really doesn’t tell you a thing. Because regardless of what this poll says, I can tell you that the majority of (nitrox) divers IRL do not test except when required by shop (when picking up tanks, analyze and fill out dive log) or the operator (on a liveaboard, for example).

I’ve included just two (of many) of my experiences below:
When I was diving Nitrox at a big name recreational op in the Bahamas, the tanks came out with a sticker on them that had the percentage of oxygen only. No date, no initials. I asked the deckhand if I could analyze the tanks (I had not brought my analyzer as it was a family trip and I was just diving recreationally a couple days). The deckhand explained to me that I did not need to analyze the tanks because they had analyzed them for me. I explain to him that I was breathing the gas so I wanted to verify the oxygen content. You would have thought I was asking to start up the compressor and fill my own tanks! Eventually, they brought the shop analyzer out and analyzed the tanks with me watching. (Point - obviously my request was atypical)

On a group trip to Indonesia, again, tanks came out with stickers with O2 percentage and nothing else. This time when I asked, however, they were happy to let me analyze my tanks, on a daily basis. However, the group leader (a DM) basically chastised me for wanting to analyze my tanks. Her reasoning? That the Nitrox was banked - so the tanks had to be right!

Similar experience at one of the best known brands in Bonaire a few years ago. They looked at me like I had two heads when I asked for their analyzer to check my cylinders. (And the mixes I was supposed to accept on faith were NOT very consistent, either.)
But before reading this thread, I would probably never have thought to analyze my air mixes, just my EAN mixes. While I am still not likely to do so for every cylinder in the future, I will probably be paying more attention to what is happening with EAN cylinders when/where I travel, and consider analyzing my air if I don't like/trust what I see. At home, I am only pumping air in my own shop, and the training quarry is well run, so I don't anticipate any added checks locally.

 

[TrimixToo]

I suppose I'm an "other."

I check any fill anyone else does. I check all my mixes. I don't check my O2 fills or my air fills because air and O2 tanks are dedicated and are never hooked up to anything other than air or O2.