Excessive Carbon Monoxide Levels Discovered in Utila Nitrox Tanks

[Trixxie]

edit - the other one I found does not register under 30PPM

no good for this application

[DandyDon]

Originally Posted by peterbj7

Is there any evidence to suggest whether the CO is sucked into the intake for the compressor, or produced within the compressor (probably by "dieseling")?

If the former than using air from an electric-powered compressor should be a lot safer than if it were powered by an internal combustion engine, unless the air intake were located in an area of high vehicular traffic....?

If the latter than there could be a variety of contributing factors - wear state of the bores/pistons/rings, age/state/type of the compressor oil, operating temperature of the compressor, design/type/state of the filters. Anything else?

All that is certainly true from what I've read on the related threads - electric safer than internal combustion, air intake source very important, wear state, age/state/type, op temp, correct filters - on the Maldives accident with 1 dead 9 injured, they were using cheaper electric filter on a gas power compressor. Add an inline monitor and for compressors on boats, keep the boat moving while compressor running to avoid CO plumes.

I wish I had been there for this one. Don't know about the state of the compressor; don't yet know if my Inst went into town to look at it - or just waited to retest.

Originally Posted by Trixxie

Wonder if this one works the same or just as well as the one you found

It's $43.99

Has anyone tried one of these yet?

(I don't think this one gives you a % reading, looks like it just alerts you if levels are too high. wonder what it's set at?)

Good find. Actually, that one would possibly suffice as good as the pricier model I have for many travel related needs that did not include breating air under 2 to 5 or more atmospheres of pressure. Looks like it's similar to the 110v plug in models many of us have in our homes, possibly set to go off around 50 ppm? The site doesn't say does it? I guess you could phone them to ask? Looks a little bulky, but possibly a good idea for every vehicle. "Over 1100 people die annually from CO poisoning caused by vehicle exhaust-Don't be one of them, Protect Yourself and your Family."

We need a monitor tester that will read below 10 ppm, I think. That example is why I plan to leave mine on 24/7, tho.

[swamp diver]

Originally Posted by DandyDon

I just today got mine as I had it shipped to my Inst for this trip. I think he use my suggestion on taking tests...
1-Turn on and drop into one gallon clear plastic bag - and I prefer the tall bags to the zip locks, altho I have not done a hands-on test yet;
2-Compress bag to push all air out, then fill bag half full from tank, twist neck with monitor face down to expose all three inlets to air, and hold for 2 minutes - use second counter on watch or whatever I think so you won't rush this.
3-Then read.

Keep in mind that there is going to be 1 to 5 ppm background CO in everyday air, maybe more - but scuba air is always supposed to be below 10 ppm.

If we can get enough divers carry these, running the tests and reporting on SB, we can get a better idea of the real situation in the tropics. Even DAN doesn't know.

I just got a PM from a friend just back from Fantasy Island Beach Resort on Roatan who'd asked the manager about their air quality control, and he was happy to show the compressor and the quarterly test results from TA: Compressed Air Testing Specialists - Makers of the AirCheck Air Sampling System - Trace Analytics I was pleasantly surprised that they do theirs, but I don't know if they have an inline monitor or scrubber?

One point of confusion in how to use the unit is that one should fill the ziplock bag with the tank air and then let the CO unit sit in that air for 90 to 120 seconds in order for the peak concentration to be read. One does not have to purge the air for two minutes into the bag as I read elsewhere. The electrochemical sensor works by diffusion so any CO will find its way into the sensor if ambient air is kept out of the bag.

Normally at a typical tropical dive site the ambient CO level especially out on the boat with the engines shut down is < 1 ppm. One will only find levels above zero in urban areas with lots of traffic, downwind of wood fires, etc. Of course if the boat's engines are running, in particular gasoline-powered inboards, then there is a high risk of CO contamination on the way to the dive site (see link below) even while underway due to the "station wagon effect."
http://www.aiha.org/TheAcademy/docum...6-mccammon.pdf
BoatUS Foundation: The Dangers of Carbon Monoxide

Fantasy Island has three compressors in a very small room with poor ventilation. There should be no ambient CO given where their intakes are located (i.e. away from boats and traffic) yet if one looks at the air test results on their web site, particularly for the hotter summer months, there is low level CO (4 to 8 ppm) in a couple tests. If there is catalyst in their filters then that would suggest upstream of the filter the CO level from dieseling of the oil would be significantly higher. If there is no catalyst or wet catalyst then one is observing direct low level CO contamination from pyrolysis of the compressor oil. High ambient heat, low flash point mineral oil, poor installations, 3 cylinder/4 stage compressors, continuous blending or membrane separation to produce nitrox, no catalyst or wet catalyst are all factors which increase the risk of internally produced carbon monoxide by the compressor which will then contaminate the tanks directly or storage banks.

[DandyDon]

Originally Posted by Trixxie

edit - the other one I found does not register under 30PPM

no good for this application

Thanks Trix, I hadn't read that far. I was guessing 50 ppm. 30 is cool for a car or motel room, and I am going to suggest that model to non-diving friends for each car as well as divers with more than one car - after I contact the company to see if they are in business and it is available. I saw there that the owner had a medical problem and the store was closed for two years, and the site has several out of date points. Where did you see 30 ppm? I can't find that.

I just have one so I'll use the smaller one I got to test tank air in my pickup, etc. I have two spare batteries that will fit it from dive computer battery replacements, and I just now tested those: 3.6 volt batterie that hit high on my 3.0 volt guage. Okay, maybe I'll get a spare new battery; they're cheap.