Use your CO analyzers

[Ron Lee]

Just so that I am clear, I take no position on CO analyzers. I do, however, take issue with claims of confirmed deaths from CO poisoning on Cozumel (where there are none) and assertions that CO poisoning incidents have occurred which have been attributed to other things (where there is no evidence of that) as reasons for them. If you decide to analyze your tanks because of verifiable statistics, or because of simple prudence, or even from general paranoia, I have no problem with it. I probably won't go to the trouble because I think the risk is low for me to encounter a poisoned air tank. Likewise, I don't take a parachute on airplanes.

The bolded text is one of my primary issues with this discussion as well. Plus the apparent lack of data to suggest what level of CO is problematic.

I am newish here and do not have years of background on previous CO discussions. So when these do come up, hard data is useful to help us learn and make informed decisions. Suggesting that missing divers drown because of undetected CO does not make a case and in my opinion is far worse that throwing out claims of "trolling."

One example, we have reported standards of 15 PPM, 10 PPM and 3 PPM of CO in various countries. Maybe there was even a 0.3 PPM. Which is right? If medical science shows that 10 PPM meets accepted standards for diving safety, is 8 PPM "safer?" How about 5 PPM. I would assume that 10 PPM has adequate margin from whatever level is "unsafe."

Then there is the issue of being a smoker which I was unaware of. Does being a smoker place a diver at a higher risk level with clean air or a tank with some level of CO less than 10 PPM? I read that a smoker exhales a level of CO that may make Don cringe....but need to find that article since it has been a while.

These discussions will come back and if the unconfirmed assertions of deaths and subclinical hits can be stopped, and actual data provided, then they will be more useful.

Another thing that may help, but may be impossible, is finding out what the various tank fillers have for ensuring tank air quality. There are systems that scrub the air of undesirable components (charcoal?), that should detect CO and alert the operator or maybe even shut the filling system down.

Are those systems properly placed, serviced, etc?

I am not opposed to the effort to improve air quality or catch bad tanks, but I suspect that we will save more divers by finding a way to make sure that buddy separations do not end up a missing/dead diver. Two cases in the last year that have far more credibility in being true that asserting that they were due to CO poisoning.

 

[theduckguru]

This link says DAN sent 10 to Coz. Scuba Diving Medical Safety Advice ? DAN | Divers Alert Network

A few of those ten analyzers apparently went over to the PDC-Tulum corridor where there was a double CO fatality in 2004. A Canadian tech diver and US military physician both died in different cave systems but had filled up at the same compressor on that day.
Alert Diver | DAN Donates Ten Gas Analyzers in Cozumel

Mossman it is pretty evident that you are more interested in using your fine wordsmith skills to obfuscate the real issue here which is CO contamination in compressed air does happen sporadically at many of the popular tropical dive destinations and has lead to confirmed CO fatalities (Tulum, Roatan, Maldives, Cabo San Lucas, Egypt, etc.). If a double fatality can happen across the channel in Tulum it can also occur on the island of Cozumel when compressors are installed improperly, maintenance is neglected, or a car backs up to the intake. If you want to believe the risk is zero then great dive on, but those of us schooled in the science of risk and probabilities know that while the risk of CO poisoning is small it is not zero and given that the health consequences of CO poisoning underwater are very high it is very rational to screen one's breathing air for this odorless contaminant prior to diving.

The accredited laboratories in the USA which receive compressed air samples from dive compressors around the globe still report a CO contamination rate of 3% to this day (see below). That 3 percent failure rate is a hard and irrefutable fact which is the best indication we have as to the frequency of CO poisoning across the industry based on thousands of samples sent in per year. Meridiano 87 sends in quarterly samples to Lawrence Factor in Florida whose lab director is quoted in the article.

If you don't want to analyze for a potentially lethal odorless contaminant known to impair the cardio-respiratory system then that is your prerogative, but for the divers who would like to take a more pro-active approach to their personal health and safety I suggest you direct your penchant for arguing elsewhere.

 

[swamp diver]

One example, we have reported standards of 15 PPM, 10 PPM and 3 PPM of CO in various countries. Maybe there was even a 0.3 PPM. Which is right? If medical science shows that 10 PPM meets accepted standards for diving safety, is 8 PPM "safer?" How about 5 PPM. I would assume that 10 PPM has adequate margin from whatever level is "unsafe."

USA CGA 7.1 Grade E 10 ppm
USA NFPA 1989 (fire fighter compressed air at 1 ata) 5 ppm
Canada CSA 275.2 (diving) 3 ppm
Canada CSA 180.1 (fire fighting) 5 ppm
Britain DVIS9 (diving) 3 ppm
Europe EN12021 (draft, diving) 5 ppm
Australia AS2299.1 (diving) 10 ppm currently discussing 5 ppm

Ambient air away from man-made sources of CO has a carbon monoxide concentration of about 0.2 ppm,...very low and almost zero. In most US and Canadian cities now away from large freeways ambient CO is running < 1 ppm at all times.

If the compressor has a catalyst bed (i.e. Hopcalite) to convert CO to CO2 the amount of CO in your tank should be zero. If there is no catalyst bed and the compressor intake is not next to a freeway or busy road the CO in the compressed air should still be < 1 ppm. Therefore when there is more than this either the compressor has added that CO from within or entrained it from a point source external to the compressor.

Dive air should have 0 ppm of CO on a properly installed and maintained compressor, but most portable and fixed monitors have a resolution and minimum detection limit of 1 ppm so if we say anything > 2 ppm one should start to ask where is that extra CO coming from.

The CO specification for diving is set for the most sensitive person in the group who will be using that air taking into account maximum pressure exposure for air and typical dive duration. The most sensitive person would be the unfit diver with undiagnosed coronary artery disease who smokes. Most of these maximum concentrations are set for commercial divers who use surface supplied air down to 50 metres (6 ATA).

Yes smoking pre-loads your red cell hemoglobin with CO and additional CO in the dive air may overwhelm the physiological mechanisms the body uses to compensate for the impaired oxygen carrying capacity. There are many factors at play such as existing chronic COHb level from smoking, acute on chronic CO exposure, depth, time, fitness, age, exertion during dive, air vs. nitrox, etc. etc.

No CO is best in one's dive air particularly if you are older, unfit, a smoker or have diagnosed heart disease. Younger fit divers can tolerate higher levels of exposure, but best not to try underwater.

 

[Ron Lee]

Most of these maximum concentrations are set for commercial divers who use surface supplied air down to 50 metres (6 ATA).

Excellent post with mucho data. Not to quibble but I still have to question the different standards such as several at 5 PPM and a US standard at 10 PPM. Sure it should be closer to zero but as a diver am I at higher risk using a 10 PPM tank versus a 5 PPM tank?

Now for a question that I should probably know but I think I took in some CO from my car exhaust so my thinking is impaired.

In the quoted text, whether the air breathed at 50 meters is surface supplied or from a scuba tank has zero difference...correct? You are still breathing 6 ATA air in either case?

 

[swamp diver]

Excellent post with mucho data. Not to quibble but I still have to question the different standards such as several at 5 PPM and a US standard at 10 PPM. Sure it should be closer to zero but as a diver am I at higher risk using a 10 PPM tank versus a 5 PPM tank?

Now for a question that I should probably know but I think I took in some CO from my car exhaust so my thinking is impaired.

In the quoted text, whether the air breathed at 50 meters is surface supplied or from a scuba tank has zero difference...correct? You are still breathing 6 ATA air in either case?

Not to get into the nitty gritty of standards development but I would place the least amount of emphasis on the Compressed Gas Association spec at 10 ppm. It is an industry-only committee (one has to pay a very healthy fee to join the committee) with no physician representation and they only update the G7.1 standard on a very long schedule while the science on the physiology of CO and its role in signalling in the human body has exploded in the last 5 years. All of the other global standard committees are a broad matrix of members from industry, academia, medicine, government and meet on a much more regular basis. In the USA I'd follow your fire fighter CO spec (NFPA 1989) and use that as a maximum for air diving.

In general yes a tank with 10 ppm will represent a higher risk than one with 5 ppm because for a commercial diver at 6 ATA for example the effective surface exposure concentration is 60 ppm and 30 ppm respectively. Non of those Montreal fire fighters dropped dead from breathing 250 ppm of CO contamination in their SCBA tanks as they were young and fit. There were symptomatic though but if you strapped one of those tanks with 250 ppm on their overweight 55 year old Captain and asked him to run a lap around the track he might have dropped dead from a heart attack. Same goes for divers. Unfit, obese, smoking diver swimming against a current may have cardiac issues with 60 ppm while young Navy Seal will just feel his fitness level impaired and recover.

No difference if contaminated compressed air is breathed from an umbilical or scuba tank at 6 ATA. The effective CO exposure will be the measured surface concentration x 6 ATA.

 

[Ron Lee]

Thanks again for useful, educating info.

In one of these discussions, my vague recollection is that part of the problem with CO is that the ascent is where the medical symptom may be manifested.

Imagine diving at 30 meters for an appropriate time with a tank that has a really bad CO level. Let us just use 250 PPM per your previous post. At 30 meters the diver is fine. The ascent is multi-level and could be 30 minutes or more.

Is it true that somewhere during the ascent that the previous exposure to high levels of CO could become apparent? I might be able to find this using google but there are people here better informed on this and they may have the answer (and source hopefully) handy.

 

[DiveNav]

..... a tank with 10 ppm will represent a higher risk than one with 5 ppm because for a commercial diver at 6 ATA for example the effective surface exposure concentration is 60 ppm and 30 ppm respectively..... .

Yes, but doesn't the increased PO2 somehow mitigate the increased CO concentration?
I can't find literature on this :depressed:

Alberto (aka eDiver)

 

[Darol]

Someone said:

It's got to be true because I said it was and look, it's on Scubaboard.

I love it when the word merchants and pundits get together and slug it out on SB...... .:boxing:
It makes a 12 hr. shift at the old refinery fly by.
Wait a minute, is that hydrocarbon I smell???

 

[DandyDon]

Yes, but doesn't the increased PO2 somehow mitigate the increased CO concentration?
I can't find literature on this :depressed:

Alberto (aka eDiver)

I think to some extent yes, but not well offsetting. And it gets worse on ascent...

Thanks again for useful, educating info.

In one of these discussions, my vague recollection is that part of the problem with CO is that the ascent is where the medical symptom may be manifested.

Imagine diving at 30 meters for an appropriate time with a tank that has a really bad CO level. Let us just use 250 PPM per your previous post. At 30 meters the diver is fine. The ascent is multi-level and could be 30 minutes or more.

Is it true that somewhere during the ascent that the previous exposure to high levels of CO could become apparent? I might be able to find this using google but there are people here better informed on this and they may have the answer (and source hopefully) handy.

I don't think he'd be all that fine at 30 meters on a 250 ppm tank with the depth equivalent of 1,000 ppm, possibly working against a current making it worse, etc. I think he'd be enough enough trouble with a 25 ppm tank. We really don't know much about the various combinations and risks as in the discovered cases here and there where CO poisoning has been confirmed, details were never made available, in part because lack of testing apparatus. And it's not the sort of thing you can expose volunteers to in a chamber as a test. Back to goats maybe...?

Nowadays, more divers are arriving with CO analyzers, if they can get to suspected tanks before they are drained, but that brings up a new challenge: If you are an innocent bystander with a CO analyzer when a suspected hit occurs in another country, how much do you want to let yourself get involved? Sorry, my imagination boggles at possibilities. I hope I would find what I could, document it well, and make the info available to the surviving loved ones, but while there - I don't know?

Getting back to your main question: As Divenav suggested, the increase in PPO2 at depth will somewhat offset the increase in PPCO, but the CO will bind with red, O2 carrying cells - not only decreasing the benefit of higher PPO2, but on ascent the O2 will offgas while the CO remains bound. This is why doctors use pressure chambers to treat all CO victims. It's like a diluted poison makes your sick so you ascend and the poison becomes more concentrated, sort of.

 

[DSR-3]

Stick to the statistics (like and "idiot")?

This is mainly for Mossman, since he like to ask hypothetical questions too, but it would be interesting to hear how others would act;

Let's say you're on the boat ride to Punta Sur, when you realize that that guy checking his tank for CO, O2, and rat turds- is none other than the DandyDon.
-You & the dive op. didn't bring any analyzer.
-He gets readings of 20ppm, 21%, and 0 from his tank.
What would you do?