My Portable CO Monitor/Tester Field Experiences .

[DandyDon]

RTFM, eh?

I did read *some* of it. I'll place it in the bathroom, that'll ensure it gets read cover to cover

Thx for the clarification.

John

Yeah, I start playing with new electronic toys before I read the manuals well, too. :blush:

 

[Seanpaul]

Hi! I am still in the states after diving in Jamaica. Just wanted to report in on my tank test. I was at the Beaches resort in Ocho Rios. Of six tanks I tested, 5 were zero and one registered 10ppm. It was interesting we had one contaminated. We hypothisized perhaps someone smoking near the intake valve, any thoughts on this? We bled that tank. Overall absolutely thrilled with the performance and ease of use with the CO monitor (I used freezer bags Dandydon) and equally happy with the air quality! The dive crew had mentioned on occasion they were getting headaches on dives to 60 ft which were long (about an hour) so I was curious to see the results.

 

[DandyDon]

Hi! I am still in the states after diving in Jamaica. Just wanted to report in on my tank test. I was at the Beaches resort in Ocho Rios. Of six tanks I tested, 5 were zero and one registered 10ppm. It was interesting we had one contaminated. We hypothisized perhaps someone smoking near the intake valve, any thoughts on this? We bled that tank. Overall absolutely thrilled with the performance and ease of use with the CO monitor (I used freezer bags Dandydon) and equally happy with the air quality! The dive crew had mentioned on occasion they were getting headaches on dives to 60 ft which were long (about an hour) so I was curious to see the results.

Interesting. I suppose it could be boring to always get a zero reading after buying, studying, learning, preparing, testing - but I hope it's more reassuring. How long did you test the high tank? I wonder if there may have been any changes in readings from the 2 minute mark to 3 or 4?

Possible causes in addition to "smoking near the intake valve" - an unforgivable mistake if so, would also include a vehicle or other liquid fuel engine, bad intake placement, or even a CO plume around the fill shack with no wind. The big failing would be lack of a scrubber and/or CO monitor with auto shut-off on the line. Did you look over their setup?

 

[bleeb]

Hi! I am still in the states after diving in Jamaica. Just wanted to report in on my tank test. I was at the Beaches resort in Ocho Rios. Of six tanks I tested, 5 were zero and one registered 10ppm. It was interesting we had one contaminated. We hypothisized perhaps someone smoking near the intake valve, any thoughts on this?

How much of cigarette smoke would have to get into the tank for it to average out at 10 ppm? I'm wondering if anyone has a feel for this.

I tried to do a back-of-envelope estimate. Someone said earlier in this thread (or the other one about CO testing) that smokers are exhaling around 60 ppm. Assuming a large 1 liter per puff, it would take roughly 360 puffs to fill an Al 80 to 10 ppm. And that's if just one tank was being filled.

So is a cigarette a realistic source of anything more than trace contamination, or should we be looking about more serious sources? I'm thinking more in general, when checking out fill stations than necessarily this particular case. Any compressor types out there have any insights to share?

 

[Seanpaul]

Interesting. I suppose it could be boring to always get a zero reading after buying, studying, learning, preparing, testing - but I hope it's more reassuring. How long did you test the high tank? I wonder if there may have been any changes in readings from the 2 minute mark to 3 or 4?

Possible causes in addition to "smoking near the intake valve" - an unforgivable mistake if so, would also include a vehicle or other liquid fuel engine, bad intake placement, or even a CO plume around the fill shack with no wind. The big failing would be lack of a scrubber and/or CO monitor with auto shut-off on the line. Did you look over their setup?

I was testing each tank at 3 minutes. There was no on line monitor, the filters had been changed mid June and no road near the air intake for a truck or other vehicle so that was why it was so perplexing. Air intake is fixed on the side of the building at about 8 feet. There was no date on the fill so it was hard to know whether this was before the filter change or not...

 

[DandyDon]

If there was no breeze, a still air plume could certainly be possible. Well, good that you knew which tanks were safe and which to reject, and good to send a strong statement to the Operators that some of us do want to check their air quality and their set-ups. It would be good if they installed an inline monitor and/or a scrubber.

My LDS lost their pick-up and trailer to a major vehicle collision last month that should have killed all but fortunately all survived with varying degrees of injuries - light ones to my friends. They've replaced almost everything quickly, and I picked up a nifty CO monitor for their trailer compressor on Ebay: A new 12 volt Fireboy-Xintex CMD-4MR Carbon Monoxide CO Alarm with auto shut-off. MSRP $200; available online for $100; I got it for less than $10!

 

[partyper]

I have received this from KWJ Engineering Inc.:
For your information, in a couple weeks we'll be announcing our new Model 300S, a Pocket CO with accessories specifically designed for use in scuba tank testing. Check back on our website, as you may want to order this kit.

 

[DandyDon]

I have received this from KWJ Engineering Inc.:
For your information, in a couple weeks we'll be announcing our new Model 300S, a Pocket CO with accessories specifically designed for use in scuba tank testing. Check back on our website, as you may want to order this kit.

Hey thanks. Dave & I discussed this idea, I gave him my suggestions, but told him I was rather happy with my current methods. Still, good to see they're interested in working with scuba divers and catering to our needs. I've had many phone chats with Dave & Oliver over this and I suspect they've talked to as many other divers as they could as well.

I'm surprised that I didn't receive the email? Hmmmmm? Well, thanks again!

 

[swamp diver]

I was testing each tank at 3 minutes. There was no on line monitor, the filters had been changed mid June and no road near the air intake for a truck or other vehicle so that was why it was so perplexing. Air intake is fixed on the side of the building at about 8 feet. There was no date on the fill so it was hard to know whether this was before the filter change or not...

If there was no obvious point source for CO (i.e. boat or vehicular exhaust) at the compressor intake and you ensured the tank CO reading was not spurious by removing the monitor and having it return to zero within a minute or two followed by a repeat reading to 10 ppm then the likely source of CO is overheated compressor oil with partial combustion.

What would not support this internal compressor source is if the operator was filling the tanks off storage banks as all the dive tanks would have the same concentration. If he was filling directly off the compressor then yes one tank could be contaminated depending on the temperature of the hot stage.
http://www.analox.net/site/content_pdfs/CarbonMonoxideInDiving.pdf

 

[swamp diver]

Don, I have had my Pocket CO unit for a good month now and have had a chance to not only try it out in many different field situations, but also to compare its performance to the BW Tech Gas Alert Extreme and the CO Expert unit albeit a 5 year old 2002 model.

I ran out of 50 ppm calibration gas and at $3/minute to run I didn't feel like purchasing another 34 liters so there are a few blanks on the chart below.

One can see that the BW Tech unit is very stable and accurate across the range of temperature and humidity the detectors were exposed to as was the CO Experts unit which is 5 years old now and has only been factory calibrated once since purchase.

The Pocket CO seems to be reasonably accurate across the temperature range possibly reading a little low with 60 percent RH, but with the 85 percent humidity there is an increased sensitivity of about 20 percent. The recovery time (time for reading to decay back to 5 ppm after CO gas removed) was significantly prolonged with the high humidity for this unit.

One interesting point for both the CO Expert and Pocket CO units is one can apply the test gas directly to the inlet holes without having the flow affect the reading as long as the flow rate is kept below 1 lpm. I tested the Pocket CO with calibration gas directly applied to the gas inlet at 0.5 and 1.0 lpm and the unit remained accurate. I suspect at higher flow rates one will get a pressure spike to the reading.

What this means is you can forget the bag technique and purchase a BCD flow restrictor, calibrate it at 1.0 lpm, and apply tank air/gas directly to the side hole. Clear 3 or 4 mm vinyl hose can be had at Home Depot or if you have access to a laboratory ask them for a few feet of Tygon tubing.

Tech Diving Ltd sells a low pressure BCD restrictor for $30 here but you will have to turn down the flow (uses hex key) to 1.0 lpm.
BC-Gas-Flow [GA-BC-Flow] - $30.45 : Tech Diving Limited, a subsidiary of Scuba Training and Technology Inc.

More to come on cross-sensitivities,....