Printable View
as a frequent recepient of outlaw caver's mixes, i appreciate very much his fastidiousness when it comes to mixing and analyzing our breathing gasses. i know that this is a very time consuming process, but when we hit the nest or diepolder or even JB, i know that i do not have to worry about what i be breathing. now if only the rest of his pathetic life was so ordered!
however, as safe and accurate they are, i have wondered about that nefarious odor of only MY mixes
Even with air or O2, if you are not analyzing you are assuming they are connected to the right whips and the correct knobs are on - you could be getting helium instead or O2 etc. You are also assuming that nothing evolved in your tanks since you used them - I wonder if that would show up on my testing if something strange did happen in there?
i do my own fills. typically i like to analyze at the shop and at the divesite right before diving.
i've caught myself doing fills where i've left the O2 open with the air (now i tend to run through an automatic check to ensure that everything is off before i open anything up to prevent that, but it could still happen). since the bank pressure of the 21% was so high and the O2 pressure was so low it didn't seem to cause much of a difference. buddies of mine have done that mistake when the pressures were closer to equal and have gotten really crazy mixes.
sometimes it takes awhile for helium mixes to settle out as well -- although typically this happens to me when everything i do goes through the booster and flow rates are really, really slow (e.g. changing half-full 30/30 into 21/35 or something silly like that). normally i put a few hundred psi of air in fairly quickly at the very end which seems to promote bulk mixing in the tank and i don't need to let it settle overnight.
The O2 and He we buy from gas suppliers is required to meet extremely high purity standards and is subject to a series of controls intended to ensure you get what you pay for. I see divers omit analyzing their O2 bottles fairly often, and while I understand the temptation in my opinion it's a very bad idea...
A gas supplier (not a dive shop) I used to use in Ohio delivered bottles of pure N2 to a nursing home, rather than the O2 that was ordered. A series of errors involving repainted bottles and inappropriate use of valve adapters allowed the nursing home to plumb it into their supplemental O2 system, killing several residents throughout the building.
So now I analyze my oxygen, just like everything else. I calibrate to dry compressed air, so don't expect it to read exactly 100.0%, but the difference between pure O2 and anything else is quite apparent. Such errors may be extremely rare, but the ultimate opportunity to prevent the consequences rests with me, the guy who's about to breathe it.
BTW, a friend made up some decals for calibration bottles, "Air - do not breathe". :)
I analyze all Nitrox, and all cylinders which come from a facility that fills Nitrox or mix. (For example, on this last trip to Mexico, I got doubles with air in them from Aquanauts -- but they come from the same fill station that does all the Nitrox, so I analyzed them, too.)
We have a couple of local shops that only fill air, and I wouldn't analyze tanks from them.
I analyze all tanks before I leave the shop with them. I then analyze them again at home.
I don't have a helium analyzer just yet, but it is in the works. So for right now it is just the O2 that gets checked a second time.
I have never forgotten the first dive in the Extended Range class that our team did at Forty Fathom's.
We failed to analyze our O2.......Dan said (actually yelled) now you're both dead.
We have never forgotten this and we ALWAYS analyze our gas independently. We forgot the analyzer once.....so we didn't dive.
Ever since I got to CCR I analyze everything (even air or O2) without exception.
Before I used to be sloppy with O2 sometimes.
I have gotten complacent with analyzing air at shops that I trust. Not anymore, just too important. Thanks for reminding me folks!
I continuous blend at home (except 50%). Sometimes I label tanks with what they are supposed to have in them just to maintain inventory. In these case I don't use a decimal point and I use a % symbol.
But before a tank gets into the truck it gets analyzed. This includes O2 although I'm not very anal about calibrating for that, 98, 99, 102% are all good to me. As long as I can tell its not 50% or He or something like that.
My biggest potential source of error is on 50%. Al40s get pretty hot during fills and to avoid much overfilling I usually top them off the next day. 1100psi of O2 but only (net) 1600psi of air gives a rich mix. Forgetting to top off isn't common but it happens.
When travelling I or my wife analzyes every tank (e.g. I haul to the car, she analyzes). Generally the mixes are low but we've had some 'hot' ones too. e.g. 41% instead of 32%EAN. Proving to me that you are rolling the dice if you don't analyze every tank. Stupid way to die too.