Cozumel Diving 2/26/12 - Had one tank read 12 ppm CO -

[swamp diver]

You are correct that citing a handful of unproven anecdotes is definitely unscientific. Also, if nitrox tanks were as routinely untested as are tanks for the presence of CO, fatalities would skyrocket. Because of the extreme risk, nitrox testing is uniform. Most tanks are tested twice, often three times or more by the time the diver starts to inhale. Uniform testing of CO might cut down on a handful of fatalities a year if that. As I've stated before, the risk of CO poisoning is less than that of an "undeserved" DCS hit. It's so low as to be barely quantifiable, and given the other unmitigated risks divers face, it just doesn't seem worthwhile for some of us to bother with an insignificant risk. Obviously YMMV.

The risk of CO poisoning may be much higher than we'd like to admit basically because no one is doing a carboxyhemoglobin (COHb) in all dive fatalities, however if you look at the Dr. Caruso’s UHMS retrospective dive fatality abstract posted earlier 3 percent of the divers whose COHb concentration was checked at death had an anomalous level. Three percent is certainly well above the frequency one would expect for a potentially lethal contaminant that is "barely quantifiable" and far greater than the risk of dying from DCS.

We can also try and assess the frequency of CO contamination in our breathing air from another direction and that is by asking the compressed gas analytical laboratories what their frequency of test failure is for CO at the 10 ppm level. These labs receive thousands of dive air samples a month from fill stations all over the globe so this number would be the best real-time indicator as to the extent of the contamination problem.


This question was posed to the labs by Bob Rossier, an ex-NASA life support systems engineer, in 1998 and 2004 and reported in the DAN Diver Alert magazine. I have attached his 2004 DAN Diver Alert article which indicates that when Lawrence Factor and TRI Laboratories, two of the largest compressed gas laboratories in the USA, were contacted and asked the frequency of CO contamination in dive air alone (fire service compressed air has a CO failure rate about 0.1 %) both labs reported independently in 2004 that the failure rate was 3 to 5 percent, an incredibly high percentage considering the high toxicity of this contaminant and potential for death in the underwater environment. In 1998 these same lab directors were asked the CO failure rate in diver compressed air and reported it was 5 to 8 percent so things have improved somewhat since that time but not by much.

The point is though that if someone told you that there was a 5 percent chance the tank of dive air you might use could contain CO at a concentration above 10 ppm I think you would be hard pressed to call that "barely quantifiable" in fact a rationale person would request that their fill station install a CO monitor or that the individual diver would purchase a personal CO analyzer.

It does not surprise me at all that we are hearing of more and more CO-contaminated tanks plus CO-related injuries and deaths as the awareness of the problem and in-field tank testing has increased 100 fold with the availability personal CO analyzers. In the end the frequency of these CO incidents in the field should reflect the rate of CO contamination identified by the labs testing the compressed air from the same field on a daily basis. Only when a COHb concentration is done in all dive fatalities will we also see the frequency of anomalous COHb levels trend towards that 3 percent level.

In 2009 I spoke with these same lab directors again and they confirmed that nothing had changed since 2004 indicating that we in the dive community still have a 3 to 5 percent chance of receiving a tank of compressed air with CO contamination > 10 ppm. The samples sent to Lawrence Factor and TRI come from all over the world so this is a global dive industry problem but worse in those geographical regions where high ambient temperatures conspire to allow poor compressor installations to overheat and intermittently burn (autoignite) the compressor oil.

If it was reported that that our national blood supply contained HIV or Hep C contamination at a rate of 3 to 5 percent not only would the population be up in arms and demand rigorous testing to eliminate that risk, but I doubt you find to many potential transfusion recipients cavalierly saying this was a negligible risk and that they would rather forgo HIV or Hep C testing and just accept the risk of contracting a potentially lethal disease.Yet sadly in the dive industry that is exactly what we still hear today despite the facts indicating the CO contamination risk is quantifiable in our dive air and runs about 3 to 5 percent.

 

[cruiser]

Even tho I was finding 5 ppm in my tanks then tho, no one wanted to borrow my CO test.

I think this reflects the industry training and standard. It's drilled into us to check and recheck our nitrox tanks, but nary a word about CO testing even though it's just as significant than nitrox testing.

 

[cruiser]

So what is an acceptable ppm for CO??

I assume 0 is the best answer of course..

Yes, 0 is the best answer. My personal limit is 3 ppm. (This is also the UK's limit on CO in tanks.)

 

[Mossman]

The point is though that if someone told you that there was a 5 percent chance the tank of dive air you might use could contain CO at a concentration above 10 ppm I think you would be hard pressed to call that "barely quantifiable" in fact a rationale person would request that their fill station install a CO monitor or that the individual diver would purchase a personal CO analyzer.

If the rate is even 3%, that means I've likely had 19 tanks with a level of over 10 ppm in my 640 dives. Really? If that's all we're worried about, then bring it on 'cause I'm still alive and breathing. However, even as late as 2010, Rossier is still recommending the "sniff test" as one method of checking a tank, though he concedes it's more accurate to use an analyzer. (Alert Diver | When Gas Goes Bad) You'd think that if it were a real concern, DAN would be all over demanding CO analyzers on every boat just as fervently as they demand emergency O2.

Mexico naturally has laxer health standards than the U.S. or other "first-world" countries. Therefore, if 10 ppm is OK for Americans (who must be naturally tougher than 5 ppm wussie Canadians), 20 ppm is probably good enough for Mexico. Besides, many of the harmful bacteria and viruses I'm ingesting in my salads and undercooked meat and fish there probably feed off the excess CO in my blood. If not, there's hardly anything in Mexico that tequila can't fix.

 

[DandyDon]

But I do agree. If CO testing was 100% uniform around the world, a handful of fatalities around the world might be avoided. I'm just not sure what cost this might have. Sure, large filling facilities like the ones in Cozumel and big dive ops like Aldora might be able to afford the necessary equipment, but many dive operations around the world aren't so well off that they can easily afford the latest gizmos. Do we put thousands of dive operations out of business in order to save a handful of divers? (Please consider that, unlike in Cozumel where there are central filling stations, most dive ops pump their own gas.) It's obviously much harder for a small six-pack dive op who can barely afford to keep up with compressor, boat, and equipment maintenance, pay captain and DM, and still try to take home anything for themselves, to install expensive in-line CO monitors. Testing individual tanks may be feasible, but still not without costs.

Even more reason for the diver to test every tank personally.

 

[TomZ]

The risk of CO poisoning may be much higher than we'd like to admit basically because no one is doing a carboxyhemoglobin (COHb) in all dive fatalities, however if you look at the Dr. Caruso’s UHMS retrospective dive fatality abstract posted earlier 3 percent of the divers whose COHb concentration was checked at death had an anomalous level. Three percent is certainly well above the frequency one would expect for a potentially lethal contaminant that is "barely quantifiable" and far greater than the risk of dying from DCS.

We can also try and assess the frequency of CO contamination in our breathing air from another direction and that is by asking the compressed gas analytical laboratories what their frequency of test failure is for CO at the 10 ppm level. These labs receive thousands of dive air samples a month from fill stations all over the globe so this number would be the best real-time indicator as to the extent of the contamination problem.


This question was posed to the labs by Bob Rossier, an ex-NASA life support systems engineer, in 1998 and 2004 and reported in the DAN Diver Alert magazine. I have attached his 2004 DAN Diver Alert article which indicates that when Lawrence Factor and TRI Laboratories, two of the largest compressed gas laboratories in the USA, were contacted and asked the frequency of CO contamination in dive air alone (fire service compressed air has a CO failure rate about 0.1 %) both labs reported independently in 2004 that the failure rate was 3 to 5 percent, an incredibly high percentage considering the high toxicity of this contaminant and potential for death in the underwater environment. In 1998 these same lab directors were asked the CO failure rate in diver compressed air and reported it was 5 to 8 percent so things have improved somewhat since that time but not by much.

The point is though that if someone told you that there was a 5 percent chance the tank of dive air you might use could contain CO at a concentration above 10 ppm I think you would be hard pressed to call that "barely quantifiable" in fact a rationale person would request that their fill station install a CO monitor or that the individual diver would purchase a personal CO analyzer.

It does not surprise me at all that we are hearing of more and more CO-contaminated tanks plus CO-related injuries and deaths as the awareness of the problem and in-field tank testing has increased 100 fold with the availability personal CO analyzers. In the end the frequency of these CO incidents in the field should reflect the rate of CO contamination identified by the labs testing the compressed air from the same field on a daily basis. Only when a COHb concentration is done in all dive fatalities will we also see the frequency of anomalous COHb levels trend towards that 3 percent level.

In 2009 I spoke with these same lab directors again and they confirmed that nothing had changed since 2004 indicating that we in the dive community still have a 3 to 5 percent chance of receiving a tank of compressed air with CO contamination > 10 ppm. The samples sent to Lawrence Factor and TRI come from all over the world so this is a global dive industry problem but worse in those geographical regions where high ambient temperatures conspire to allow poor compressor installations to overheat and intermittently burn (autoignite) the compressor oil.

If it was reported that that our national blood supply contained HIV or Hep C contamination at a rate of 3 to 5 percent not only would the population be up in arms and demand rigorous testing to eliminate that risk, but I doubt you find to many potential transfusion recipients cavalierly saying this was a negligible risk and that they would rather forgo HIV or Hep C testing and just accept the risk of contracting a potentially lethal disease.Yet sadly in the dive industry that is exactly what we still hear today despite the facts indicating the CO contamination risk is quantifiable in our dive air and runs about 3 to 5 percent.

Pfffffttttt. You and those darned facts.

 

[Mossman]

Even more reason for the diver to test every tank personally.

Even better for the diver to bring his own tanks and compressor.

 

[swamp diver]

If the rate is even 3%, that means I've likely had 19 tanks with a level of over 10 ppm in my 640 dives. Really? If that's all we're worried about, then bring it on 'cause I'm still alive and breathing. However, even as late as 2010, Rossier is still recommending the "sniff test" as one method of checking a tank, though he concedes it's more accurate to use an analyzer. (Alert Diver | When Gas Goes Bad) You'd think that if it were a real concern, DAN would be all over demanding CO analyzers on every boat just as fervently as they demand emergency O2.

Mexico naturally has laxer health standards than the U.S. or other "first-world" countries. Therefore, if 10 ppm is OK for Americans (who must be naturally tougher than 5 ppm wussie Canadians), 20 ppm is probably good enough for Mexico. Besides, many of the harmful bacteria and viruses I'm ingesting in my salads and undercooked meat and fish there probably feed off the excess CO in my blood. If not, there's hardly anything in Mexico that tequila can't fix.

I trust you are aware that the partial pressure ramifications of breathing 20 ppm CO at 130 feet means the surface equivalent concentration and therefore toxicity is 5 ata x 20 ppm= 100 ppm. If you are a fit 20 year old you're right you likely will get off lightly with only a very noticeable drop in your exercise capacity. If you are 60 years old, obese, with occult coronary artery disease this concentration may precipitate angina and a heart attack more so if working hard. Should the diver drown the coroner will conclude, unless the tank is analyzed for CO or a COHb is done on the blood (very unlikely in Mexico), that the death was due to myocardial infarction. Carbon monoxide won't even enter the analysis as the root cause.Remember though that those who set the CO specification for these various diver breathing air standards must do so for the "most sensitive" person in the diving population which today now includes many divers with diabetes or previous heart attacks both high risk groups for CO exposure complications.

Smelling one's air for odor is not going to detect CO directly however it may detect other proxy contaminants such as hydrocarbons which were produced during an oil flash over or entrained IC engine exhaust. Of course if the activated charcoal bed in the filter is new and functioning it will likely remove any odor and once again leave only the odorless CO in the fill.

I agree with you that DAN should insist that there are CO analyzers on each boat and that the training agencies should insist that all their affiliate shops purchase an inexpensive $1200 CO compressor monitor. The cost of a CO compressor monitor relative to the dive operation's total expenses would be minimal. The 64,000 dollar question and the real elephant in the room is why has this not happened??? As usual if one follows the money it reveals that some of DAN's largest sources of corporate donations come from the training agencies. I'm sure you can figure out the rest. All this talk of CO contamination in dive air is bad for business and DAN's corporate financial priorities trump the membership's safety priorities although this may be changing as the extent of the CO problem becomes more apparent.
Divers Alert Network

Us wussie Canadians have actually followed the British lead and dropped our maximum CO exposure for air diving to 3 ppm as of 2011. I should remind you though that the 2008 CO specification for your US firefighters' compressed breathing air, who use this SCBA air at only one atmosphere, is currently 5 ppm. Now if we divide that by 5 ATA for recreational diving you probably don't want any CO in your breathing air.

 

[markmantei]

If the rate is even 3%, that means I've likely had 19 tanks with a level of over 10 ppm in my 640 dives. Really? If that's all we're worried about, then bring it on 'cause I'm still alive and breathing. However, even as late as 2010, Rossier is still recommending the "sniff test" as one method of checking a tank, though he concedes it's more accurate to use an analyzer. (Alert Diver | When Gas Goes Bad) You'd think that if it were a real concern, DAN would be all over demanding CO analyzers on every boat just as fervently as they demand emergency O2.

Mexico naturally has laxer health standards than the U.S. or other "first-world" countries. Therefore, if 10 ppm is OK for Americans (who must be naturally tougher than 5 ppm wussie Canadians), 20 ppm is probably good enough for Mexico. Besides, many of the harmful bacteria and viruses I'm ingesting in my salads and undercooked meat and fish there probably feed off the excess CO in my blood. If not, there's hardly anything in Mexico that tequila can't fix.

It is clear that you are unconcerned with the risk that CO poses. That's fine, the same way it is fine if someone wants to do bounce dives to 200ft on AL80's, people have done it and survived you know, doesn't make it safe. What's unclear in all of this is why you feel the need to insist that everyone else who feels differently is wrong for doing so.

DAN is starting to come around to the dangers of CO, its why they were involved in getting inline CO monitors donated to ops in Quintana Roo. If they felt it was unimportant do you think they would bother getting $50,000 worth of equipment installed?

Don't let facts get in the way of your argument now....

 

[Mossman]

I trust you are aware that the partial pressure ramifications of breathing 20 ppm CO at 130 feet means the surface equivalent concentration and therefore toxicity is 5 ata x 20 ppm= 100 ppm. If you are a fit 20 year old you're right you likely will get off lightly with only a very noticeable drop in your exercise capacity. If you are 60 years old, obese, with occult coronary artery disease this concentration may precipitate angina and a heart attack more so if working hard. Should the diver drown the coroner will conclude, unless the tank is analyzed for CO or a COHb is done on the blood (very unlikely in Mexico), that the death was due to myocardial infarction. Carbon monoxide won't even enter the analysis as the root cause.Remember though that those who set the CO specification for these various diver breathing air standards must do so for the "most sensitive" person in the diving population which today now includes many divers with diabetes or previous heart attacks both high risk groups for CO exposure complications.

OK, so until I'm 60 years old, obese, with occult coronary artery disease, I'll not worry about analyzing for CO. I've still got a few good years left and a few pounds to gain.