Need for air tank o2 analysis

[diverdoug1]

I do about 5 liveaboard trips per year, and observed a near miss during one of them last year. Busy dive deck scenario, tanks being filled between dives. I watched one of the crew hook up the nitrox fill whip to an air tank, and start to fill it. I called attention to it, and the DM sheepishly said "oops". This brings about the question, should divers be checking the o2 content of their tanks, even when not diving nitrox? Just to state the ovious for those divers who not aware of the possible lethal ramifications of this DM's error, having nitrox (with it's higher o2 content) in a tank thought to hold air, can cause a diver to have a seizure while diving if he exceeds a certain depth. So, when nitrox is being pumped in the vecinity of your air tank, should you be analyzing your "air" tank? I know that I have started doing this on all tanks I dive with.

 

[hg frogman]

So, when nitrox is being pumped in the vicinity of your air tank, should you be analyzing your "air" tank?

Yes. What you describe has a low, but non-zero, probability of happening.

In my opinion, though, this need for analysing one's air applies mostly to dives planned significantly deeper than 18 meters/60 feet.

Or to very old fills (O2 percentage may decrease due to oxydation of the tank).


(By the way, better also smell and taste your air systematically before diving, because poisoning does happen; I learned it the hard way. I know that CO has no smell and no taste (there is another thread about it) but a lot of other nasty stuff do smell or taste : oil, chemicals, etc. No hijacking intended, back to the topic).

 

[swamp diver]

We had just that incident here a year or so ago. Banked 32 percent and basic open water students all ended up with various mixes < 32% depending on amount of remaining air in tank prior to accidental nitrox fill. Only found incidentally when instructor was playing with his O2 analyzer after dive. Not a big deal since students remained < 60 feet, but one could see where this situation could be problematic.

Teenage tank filler who was careless and was not nitrox certified.

 

[diverdoug1]

Yes, I would not be so concerned if it was a shallow, dive, other than to keep tabs on the "quality control" of the tank fills, and to give the crew on the dive deck a heads up that it is a potential issue. I just posted this to give other divers food for thought about a potential area to check. I belive in self sufficiency, and this is an issue I never gave much thought to.

 

[diverdoug1]

I am goig to give this a bump, so I can get the Monday morning quarterbacks to weigh in on it.

 

[Bronson]

wOW! I have never heard of this happenning 'cause all the places i dive charge for Nitrox and would never give it away for free. Scarry and has me thinking....

 

[boulderjohn]

A bunch of us are going on a trip in a couple of days, and in the next few days we will be filling tanks in preparation. Because of the complicated dive plans we will be using, we will be doing all kinds of fills. All of this will be done through partial pressure blending. If you ever see this being done and realize how many steps are involved, you will realize that it is all too easy for someone to make a mistake, despite all the proper precautions being taken to prevent it. Consequently, we analyze every tank we use before diving, no matter what is supposed to be in it.

At the other extreme is what was described here. In this case, you have a crew member simply filling tanks, putting air in some and nitrox in the other. He or she does this mind numbing task hurriedly after every dive. I would say that this simple task has an even greater possibility for error.

 

[diverdoug1]

Now on dive trips, I frequently get funny looks from the dive crew when using the o2 analyzer on my air tank. By the end of the week, a number of other divers were also were also checking their air tanks.

 

[liuk3]

I always try to remember to analyze and label my cylinder(s) before diving it even if it is only air which is being pumped into it. It's just good practice, and the small act could save your life. It is definitely worth investing in an O2 analyzer for yourself, especially if you dive frequently.

 

[H2O 70]

On a live aboard in 2006 my tank was accidentally filled with Nitrox. The boat offered 32% and air. I had returned to my gear because I needed my computer. My tank was hooked up to a green whip. I point it out to one of the DM's. He bleed the tank and refilled with air. It does happen.

The MOD of 32% at 1.6 ppO₂ is 132fsw. My tank had 400-500 psi of air in it topped off with 32%, I'm not going to do the math, put I probably had closer to 27-28% which at a 1.6 ppO₂ put the MOD closer to 162fsw.

All of our dives were within recreational limits.

I'm not making excuses for the dive boat because they made a mistake. I my situation the reality of injury was low.

It did emphasize to me the importance of actually seeing what whip is hooked up to my tank and it made me get El Cheapo from Oxycheq.