CO Detected

[kelemvor]

So I recently got a cootoo, and was basically playing with it. I decided to re-analyze the "fleet" in my garage. 7 tanks. I had previously analyzed for nitrox content, but I usually don't check LDS fills for CO.

I found 2 tanks with 1ppm on cootoo and 1 tanks with 2ppm on cootoo. I confirmed the 1ppm reading with my analox Eii CO, but only got 1ppm with the analox on the tank that read 2ppm with cootoo.

The tanks have been sitting for several months with varying nitrox mixes (all somewhat close to 32% though). The tanks registered approximately what I had written on the label from the fill analysis.

So... does this mean for certain I got a bad fill?

 

[Lorenzoid]

It depends on how one defines "bad." I read that something like 0.1 ppm is average for the atmosphere--so, nowhere near a compressor or other source of CO. True "zero" seems like it would be difficult to achieve, given the realities of how and where tanks are filled. From what others have said on the subject in previous threads, it seems a reading of 1-3 ppm is not unusual for a fill. So, is that "bad"? I assume you have seen this currently active thread:

How Much CO is divable

 

[kelemvor]

Yeah, I've read the thread. I was wondering more along the lines of whether or not I should say something to the LDS.

 

[BertStevens]

I started the How Much CO is Divable thread. While I'm not ready to reveal my personal limit yet (I want to hear others opinions first), I will remind you that in the USA, 10 ppm is allowable and 3ppm is allowed in the UK. So your results are below minimums.

Can zero be achieved? From other posts, I believe it can. Several scubaboard.com members report getting board finding zero on tank after tank. Which is a good thing! Should you tell your shop? YES! It lets them know you are watching and they'd better stay on top of it. It also could also prompt them to prevent a problem before it appears.

Would I dive the tanks? You'll have to wait for my decision on my thread! (You didn't think I'd tell did you?)

 

[kelemvor]

Can zero be achieved? From other posts, I believe it can. Several scubaboard.com members report getting board finding zero on tank after tank. Which is a good thing! Should you tell your shop? YES! It lets them know you are watching and they'd better stay on top of it. It also could also prompt them to prevent a problem before it appears.

Would I dive the tanks? You'll have to wait for my decision on my thread! (You didn't think I'd tell did you?)

Yes, it definitely can. 4 of the tanks have 0ppm in them with both my testers. I tested a LOT of tanks in cozumel last summer and got 0ppm on all tanks.

I don't think I'm going to dive these, fills are cheap. My guess is he'll refill them for free anyway.

 

[Lorenzoid]

4 of the tanks have 0ppm in them with both my testers. I tested a LOT of tanks in cozumel last summer and got 0ppm on all tanks.

Then that's all I would tell them. I wouldn't tell my LDS that they "gave me a bad fill." I would just let them know that some tanks read "0" while others read between "1" and "2" using my two different CO analyzers, and see what the LDS considers their threshold for a "bad fill." I guess, to me, it's more a matter of how it's phrased and what I intend to accomplish. If I think their average fill is too high but they do not, then I would probably take my business elsewhere rather than waste my time rejecting half the fills they offer me.

 

[DiveNav]

....... I found 2 tanks with 1ppm on cootoo and 1 tanks with 2ppm on cootoo. I confirmed the 1ppm reading with my analox Eii CO, but only got 1ppm with the analox on the tank that read 2ppm with cootoo.....

Is it 2ppm? Or is it 1.5ppm (then rounded up to 2ppm by the display) ?

Maybe the Analox is measuring 1.2ppm but displaying 1ppm and cootwo is measuring 1.5ppm but displaying 2ppm. In this scenario the difference between the 2 analyzers is very small ...

Definitely there is something wrong with those 3 tanks that is worth investigate.

 

[Mr Carcharodon]

So what is the precision of the measurements? If you calibrate and remeasure do you get the same answer? Could you just be detecting background CO for your environment? Acceptable limits are anywhere from 2 to 20 ppm.

 

[kelemvor]

I tested all the tanks twice with each tester (4 tests per tank total) and the results were extremely consistent. I talked to the LDS. He's going to change his filters in the morning and check out his whole system.

 

[JohnnyC]

Why not suggest he plumb in and in-line CO monitor and then he doesn't need to rely on his customers to catch a failing filter stack.