Carbon Monoxide: Near Miss?

[nadwidny]

Maybe a little off, could they have further reduced with filters to remove residual CO.

You should only need one filter to take out the CO.

 

[RedyTedy]

I am surprised that you didn't take your tester when you change Ops for the day.

After that incident, I made sure to take the tester to the other diveshop! I tested all of the tanks we were going to use (they were all 0ppm) before lending it to the original place.

Also I'm pretty confident the sensor was calibrated, as I had used this trip as an excuse to buy a CO tester, so it was factory calibrated from Divenav. Holding my breath then breathing out into the sensor gave ~2-5ppm which would be expected.

 

[DandyDon]

Also I'm pretty confident the sensor was calibrated, as I had used this trip as an excuse to buy a CO tester, so it was factory calibrated from Divenav.

I think I have to run the self-calibration every day with mine. You probably did those steps to get it going even tho you may not have fully understood your new unit. All of your other experiences described with it sound in line. Glad your other Op had clean tanks and you got your primary Op to clean up their gases.

 

[Pearlman]

I think I have to run the self-calibration every day with mine.

I'm curious - How does one calibrate these units daily on the field? Does it not require specialized equipment?

P

 

[RedyTedy]

I think I have to run the self-calibration every day with mine. You probably did those steps to get it going even tho you may not have fully understood your new unit. All of your other experiences described with it sound in line. Glad your other Op had clean tanks and you got your primary Op to clean up their gases.

I'm very paranoid about safety and read through the manual. The Cootwo device only required daily calibration for O2, not CO (and it will prompt you to calibrate it after expired). There's no option to even calibrate the CO sensor without reference gases on hand.

 

[DandyDon]

I'm curious - How does one calibrate these units daily on the field? Does it not require specialized equipment?

Sorry, I had it wrong. It's Oxygen that one must calibrate for this unit daily.

I'm very paranoid about safety and read through the manual. The Cootwo device only required daily calibration for O2, not CO (and it will prompt you to calibrate it after expired). There's no option to even calibrate the CO sensor without reference gases on hand.

Correct! My memory failed me on that detail, I haven't used mine since August, and it'd take me a while to charge the battery so I didn't get mine out. Thanks for the correction, and yeah I think you handled the CO testing very well.

 

[Couv]

Thank you to the OP for his report.

@DandyDon I have 2 questions if I may.
1. What is the CO level at which you would refuse a tank even if it meant no dive?

Next question is location specific. I am a regular to Cozumel too.
2. On the island, have you found tanks with levels of CO that you found unacceptable? If so, which shops? If you'd rather not say openly, would you PM the answer please.

BTW I know most shops get their fills from only a couple of sources, however I feel this is still an important question. I've recently purchased a CO detector mainly for a joint compressor venture with my neighbor.

TIA,

Couv

 

[rjack321]

Thank you to the OP for his report.

@DandyDon I have 2 questions if I may.
1. What is the CO level at which you would refuse a tank even if it meant no dive?

The answer is "none" but the reality is that you have to work within the accuracy and precision of the instrument which is usually 2 or 3 ppm. And you have to accept the fact that if you choose to do "just a shallow dive" with a tank that has measurable CO, your instrument could be wrong or inaccurate, and was never designed as a precision life safety device in the first place. So 15 ppm could really be 45 ppm or worse. Using it to confirm you have no CO is quite a different role and perspective than trying to verify that you have an "acceptable" amount of CO.

Canadian and EU gas standards specify a MAX of 5ppm
USA standards are much older and still have a max of 10 ppm which is widely considered to be too high.

I use 2ppm. But in 16 years, I have only ever had a CO detection at all when my wife backed the truck up close to the intake 14 years ago. I had a continuous CO meter in line with the compressor output at the time so it registered a hit for ~2mins. Automotive exhaust has CO in percent quantities... I have switched to just testing every tank.

 

[DandyDon]

I'm still humbled by my confusion over the daily calibration of the CooTwo. Yeah, we all make mistakes but who likes to be caught in one, in print, on SB. Oh well. It's such a fine unit, and I hate that the manufacturer closed, but glad that a servicing agency has volunteered to replace sensors and calibrate as needed as such is required every other year or so.

@DandyDon I have 2 questions if I may.
1. What is the CO level at which you would refuse a tank even if it meant no dive?

rjack321 gave a very good answer already. There should be no CO, but how confident are you in your unit and your abilities to test in the 0.0000001 range? Most of my tests are done after already boarding the boat and on the way to the way to drop point so it's kinda late in show to be calling a stop and insulting your Op's fill station. Drama is of course a possibility.

Then there the chance that I will actually risk diving at higher levels than I would advise to others, which is probably true. I have dived some tanks up to 5 ppm at times but not deep. Even tho the US limit is 10 ppm, and the simple numbers of saying a 10 ppm tank is like breathing 40 ppm at 130 feet deep which shouldn't be harmful for a short exposure - it's really more complicated than that. When it's your boat trip and dive to refuse, you have to feel confident about standing your ground and sitting the dive out hoping that the braver/less careful divers return from the dive ok, so pick a number between 3 and 10 and live to dive another day.

Next question is location specific. I am a regular to Cozumel too.
2. On the island, have you found tanks with levels of CO that you found unacceptable? If so, which shops? If you'd rather not say openly, would you PM the answer please.

Just once, and I turned the boat around to dive shallower reefs. It was my last day of a trip and I was really looking forward to diving Cathedral, but I refused - and the Op and rest of the divers were cooperative enough. I think that the main fill shacks there are aware that several of us vocal SB members are testing so are now trying harder to give us clean tanks, but there have been enough failures reported over the years that I certainly wouldn't stop testing - every tank! I have seen other readings that I didn't like in Roatan and the US. It can be boring testing tanks when you get zero after zero as you should always, until you find your first bad tank.

 

[Saniflush]

Thanks to the OP for the recounting of your experience and all the others who have chimed in.
A CO tester is my next buy.