Who DOESN'T analyze their gas?

[jcr]

I find it comical when I see people mark their tanks to the .1 percent of O2, you don't think our recreational analyzers are that accurate do you?

It may be comical but it lets my dive buddy know that I actually analyzed the tank rather just wrote down what I think it is. I see several advantages with no real downside.

[PfcAJ]

Who ever said to calibrate off a tank of who knows what? Calibrate to a tank of air; it'll be dry, and not likely to be at 90 F.

Most shops I've been to have a tank of 'air' just sittin there. You really don't know whats in it. Could be air. Could be 24%. Could be somethin' goofy like 18%. Who knows? Calibrating with atmospheric air is always yields 21% +/- 1%.

I always mark to x.x% though. Easy to have a label requesting 50% get confused with an analysis for 50%. Writing '50.4%' works to eliminate confusion between the two options.

[Dsix36]

Some of the analyzers available today automatically compensate for temp and humidity. In S. Florida as a general rule, setting the analyzer to 20.6 will almost always be too close to cause any concern.

Not to mention any names, but ask Tienuts why he does/ does not analyze tanks.

[Jax]

With ambient air at least you know the o2 within a percentage point. +/-1% is good enough for anything scuba.

Calibrating off a tank of who knows what, you're shooting in the dark.

Unless you are somewhere where the ambient air is .17%.

[FW]

Who ever said to calibrate off a tank of who knows what? ...

JahJahwarrior did, and you quoted him. I would have to agree with JahJah, and wouldn't trust a tank of "who knows what", just because it was sitting at some shop, unmarked.

...the shop employee wanted me to calibrate with an unmarked tank supposedly full of air next to the analyzer...

[PfcAJ]

Unless you are somewhere where the ambient air is .17%.

And where exactly would that be?

.17% isn't enough to sustain life. And if you meant 17%, I can't think of a place on earth where you would be scuba diving and have a hypoxic situation around you. Even at altitude, where there is 'less oxygen', the proportions remain constant, just at lower pressure.

[tursiops]

JahJahwarrior did, and you quoted him. I would have to agree with JahJah, and wouldn't trust a tank of "who knows what", just because it was sitting at some shop, unmarked.

You're right, I did quote him. I guess in the spirit of don't trust anyone or anything, I should assume that the tank of air sitting there for calibration purposes is not actually air. I guess I should also not believe the CO content is zero, that it is N2 mixed with the O2 and not CO2 in the "nitrox," and that the floor I'm standing on isn't going to give way and drop me into a pit underneath. Oh, wait, THAT actually happens... Hmmm.

[Moonglow]

http://www.cavediver.net/forum/showt...nalyze?p=51172

[Sludge]

Attachment 9102

My Scubapro analyzer came with one of these cards, and I got a thermometer for the dive trailer that gives humidity, so that's what I do. (In the summer, 90°F with 90% relative humidity yields 20.0% FO2 in ambient air.)

[Jax]

And where exactly would that be?

.17% isn't enough to sustain life. And if you meant 17%, I can't think of a place on earth where you would be scuba diving and have a hypoxic situation around you. Even at altitude, where there is 'less oxygen', the proportions remain constant, just at lower pressure.

First, all O2 analyzers actually measure the PPO2, and convert it into a percentage.

Imagine my surprise firing up my "new to me" Predator to find it flashing a red 17 PPO2! I lived at 5000 feet at the time.

So, conversation with Shearwater: All "barometric pressures reported by weather agencies are normalized for the area.".

Now that I moved into town, my Petrel reports .18 . . .

BTW, the Army requires all transferees to have at least 80 days on station before administering a PT test, because it takes time to build the red blood cells to carry the required O2.