Testing your breathing Gases Prior to Diving

[Gren]

Just to beat this dead horse a little but more...

Both camps push this a little but too far, if you own your tanks, and always get them filled at the same shop or two, and those shops only do air, you probably don't need to analyze your tanks.

If on the other hand, you rent tanks OR go to shops that do many different types of fills, OR go to as new shop, your odds of getting something unexpected go up. It's your choice whether or not to analyze.

 

[elan]

So lets look at this scenario - the shop only fills air. you bring your tank to the shop with 100 psi in it and ask for air. 5 mins later another guy brings an unmarked cylinder filled with pure O2 to 2000 psi right after the dive and asks to top it up with air. Never tells the shop it has pure O2.
The shop guy connects the whips , opens the valves and simply equalizes the tanks (yes they were a bit cheap and do not have check valves in every whip) Then happily fills both tanks with air.
A day later you both come and pick your tanks and you are both happy campers.
next dive you dive your "air" to 130 ft fighting in the current and TOX because what you thought was air is in fact now a mix of 50 percent! and you dive it to 2.5 ppo2.

I hope those of you who say that analysis is an overkill if I only fill air understand that this scenario has a much higher probability than when aliens steal some nitrogen from your tank and replace it with pure O2 in realtime while you are doing the same dive and you have analyzed the gas and properly marked the cylinder

 

[PfcAJ]

Elan, the above situation is possible, but highly improbable. There are so many 'ifs' in your scenario.

If your tank has 100psi. If the other guys tank has 2000psi. If the guy doesn't say the tank has o2 in it. If the shop attendant equalizes them. If the whips don't have check valves. If you dive it to 130ft in a current.

Lets be real man, that scenario is pretty far out, even for scubaboard.

 

[elan]

Elan, the above situation is possible, but highly improbable. There are so many 'ifs' in your scenario.

If your tank has 100psi. If the other guys tank has 2000psi. If the guy doesn't say the tank has o2 in it. If the shop attendant equalizes them. If the whips don't have check valves. If you dive it to 130ft in a current.

Lets be real man, that scenario is pretty far out, even for scubaboard.

Nah, it should not be 50% at 130 in a current. I believe last year or a year before we had a guy toxed at 140ft on 36% in still water. He survived thanks God.
My situation is a bit overblown I agree but my point was that it is still possible to get a non air fill in the shop that only fills air. It might not be that obvious for those guys who never had a chance to fill the tanks themselves. So this odd O2/high o2 nitrox tank becomes that bullet in the russian rulette. You are pretty sure the gun is empty because you have unloaded it but that guy has put a bullet when you went to pee for a five mins

BTW I rarely see check valves on the whips in local shops here they mostly limit them to the supply lines. Equalizing the tanks is fairly common practice from what I have seen around. Most of the guys though bother to analyze what is inside but its a human factor that we rely upon here. Simple check of the tank upon pickup excludes this stuff
I fill the tanks myself most of the time and although I know exactly what I'm pumping I always analyze at the end.

 

[jadairiii]

Lets be real man, that scenario is pretty far out, even for scubaboard.

Helped with a training/meet and greet dive at a local lake, max depth about 40', but, because we always check our gases, we followed our protocol and did it.

Enter new (but experienced) diver to the group, all his own gear and tanks, as he is suiting up, my buddy asks him if he as checked is gas, he say, no, but not to worry, it is air. He knows this to be a fact, no way it is anything but air. We say, lets check anyway. Surprise, surprise, surprise, analyzes much higher than air! But he was SO sure.

Do what ever you want, but understand none of us are perfect.

 

[nimoh]

there are many far fetched scenarios that could put the wrong mix in your tanks, there are many not so far fetched scenarios. Either way, you need to ask yourself am I willing to bet my life on this mix being correct?

and similarly, am I willing to bet my life on this tank being CO free?

 

[chrpai]

So let's see how many shops start requiring O2 and CO analyzers as required gear for O/W classes along with an explanation that diving is dangerous and you can't expect shops to correctly fill air tanks. Because that's the ramification of all this talk.

 

[nimoh]

So let's see how many shops start requiring O2 and CO analyzers as required gear for O/W classes along with an explanation that diving is dangerous and you can't expect shops to correctly fill air tanks. Because that's the ramification of all this talk.

well, the analyzers wouldn't be required, as students could use the shops analyzers, however I agree that I don't see this happening any time soon.

GUE requires tank analysis for O2 in their recreational program, but then, students are diving 32% all dives.

 

[chrpai]

well, the analyzers wouldn't be required, as students could use the shops analyzers, however I agree that I don't see this happening any time soon.

Not the way people have been saying it. They have been saying to analyze again on-site and that it's a team responsibility so you have to have the equipment at the dive site.

 

[nimoh]

Not the way people have been saying it. They have been saying to analyze again on-site and that it's a team responsibility so you have to have the equipment at the dive site.

I went back and read a few posts, and now I see that.

For me personally, if I asked for air, banked/membrane nitrox, or even continuous blend trimix, and analyzed it at the shop, I would be fine with that. If partial pressure filling is used, I would prefer to analyze it on site in order to shake the tanks up a bit on the drive over.

For some reason, requiring all OW students to analyze their own tanks seems like overkill to me, even though I analyze every tank for O2. I currently do not have a CO tester, and don't test for CO locally, but when I travel, I take a few of those disposable testers.