tmassey
Contributor
For tech divers, the two leading causes of death are diving deeper than your training and diving with the incorrect gas. That means, that for the most experienced divers, one of the most effective ways to remove one of the largest risks they face is simple: analyze every tank, every time. And really, this is *NOT* a hard barrier to achieve to remove a pretty big risk!
Now that I stop and I think about it, I've never heard of someone dying from diving with the wrong gas that wasn't one of two situations: grabbing a gas with *way* too little oxygen (as in Argon for suit inflation), or grabbing a gas with *way* too much oxygen (as in pure O2). Both of these are very easily deadly. But *neither* of these are relevant in a recreational setting.
What about the gasses that *are* likely to be around a recreational setting? There have been other threads recently about 'what level of PO2 is too high?' and the general answer is that you'd have to work to kill yourself at e.g. 2.0. There's no *way* I'd try to dive that, but the odds of this actually causing OxTox is not substantial. But it's *not* zero -- or even near zero.
Combining all of this, it means that even if you're pushing the recreational limits, it is really pretty unlikely to cause a problem no matter *what* recreational mix you happen to grab. Even EAN40 (a pretty rare bottom mix) at 132 feet (at the limit of recreational levels) is only PO2 of 2.0. Again, *far* from smart, but not immediately deadly.
So we've seen that the odds of killing yourself are pretty small. So does that mean that analyzing your tanks is overrated or unnecessary? Well... while the risk is small, the consequences are *very* high: a high degree of likelihood of death if OxTox *does* happen. And the cost to prevent that is *very* small: once you're experienced, analyzing your tanks takes about 60 seconds longer than it will to find the stupid analyzer. *That* is by *far* the hardest part of the entire operation -- which is why so many of us own our own analyzers!
An analyzer is only $200 or so, last for a few years and are relatively small or light. The O2 sensor will wear out (they *all* use a variation of the exact same sensor) that costs between $70 and $100, so at that point if you bought one of the tiny compact all-in-one ones, you might as well just replace it... But borrowing an analyzer is pretty easy, too. The boat *should * have one, or just keep your eyes open. *SOMEONE* on that boat will analyze a tank: just ask to borrow it for a sec. Seeing as it's in their hands, they'll likely be happy to help: like I said, it can't take 60 seconds to analyze a tank when you have the analyzer right there. They'll probably do it for you right in front of you.
Now all of this is from the perspective of death by OxTox. But that is *NOT* the main reason why *recreational* divers should analyze. For them, the reason to analyze is to make sure you got the gas you're supposed to have. The danger is the *opposite* of OxTox: getting air when you're supposed to have Nitrox. If you dive thinking you're breathing EAN32 and take it to the edge of NDL four times in a day, yet you were really breathing air... You were in *zero* danger from OxTox because air is *safer*. But you are in much greater danger of *DCS*: air has a lot more nitrogen...
Rarely have I had a mix off far enough to matter: the book says that Nitrox can be off by as much as 2 percent! (Oxygen sensors aren't terribly precise...) But I absolutely *have* been given the completely wrong gas (air for EAN32 or vice-versa, usually wrongly given air).
So it doesn't matter. Rec diving, tech diving, whatever. Every tank. Every time. 60 seconds of effort protects against all of these risks. Just do it!
