I'll take the role of devil's advocate here and question the logic of CO testing. This isn't to say that CO isn't a real risk. It is, but with all due respect to Dandy Don and others, how would you implement a testing program? (Don is right; filling stations should do this, but how would you know if they did or didn't).
Would you test every tank? Would you also verify the Oxygen percentage of air fills, in case a EAN 36 fill got mixed in? Would you turn tanks over & shake to test for loose debris which could clog your regs filter? At some point you have to prioritize risks & focus on the most real ones first. If you try to address EVERY possible risk, you'll get distracted & miss critical ones. You need to have faith in systems (and in some cases to verify adherence to those systems) to protect you from risk.
I'm curious as to how many readers of this thread, who have oil or gas heat, own or will buy CO detectors for their homes where the threat of CO poisoning is much greater. In a study years ago, folks were asked about safety fears. It turns out that the perveived fears when ranked are almost directly opposite actual risks ranked statistically.
Again, I'm only being the devil's advocate here, and don't want to trivialize the CO risk, just trying to inject a sense of proportion.
Good questions and we always need a devil's advocate
The problem with CO as compared with some of the other contaminants is it is odorless, tasteless, and irritantless and has very high inhalational toxicity particularly as the partial pressure increases with depth. While smelling one's air is always a good idea it is not going to detect low levels of carbon monoxide which may not present a problem at 1 atm, but in the sensitive diver will cause injury at depth.
I noticed on the CO-Cop web site under FAQ's that this lab states about 0.1% of samples they receive are at "dangerous levels" as opposed to the same lab which also reports in the DAN article a 3 percent failure rate for CO contamination at the 10 ppm CGA Grade E cutoff. So we likely have about 3 percent of fills which may have CO in the lower 10 to 30 ppm range, but every one in a thousand samples taken may have a level > 50 ppm which can kill you if at sufficient depth, exertion levels, smoking beforehand, etc. I suspect the distribution is not even geographically and there is a much higher frequency of contamination at the tropical dive destinations due to the high ambient heat.
I don't know about you but if someone told me that dive air has a failure rate of 0.1 percent for carbon monoxide at "dangerous levels" and that contaminant is undetectable using our normal human senses I am quite sure I would not want to play with a one in a thousand odds underwater as at some point I could be the unlucky one. In order therefore to identify that one in a thousand sample and reduce this exposure risk to as low a level as possible some sort of reliable, cost-effective, air quality testing program must be instituted by the fill station selling the diver his or her compressed breathing air .
We already have a recognized testing program advocated by PADI which is to test air quality on a quarterly basis. The problem is the resorts and operators are not following the guidelines and that places you and I at risk. If we supplemented this quarterly testing with real-time CO monitoring then the risk of contaminated air, in particular that one in a thousand potentially lethal risk from CO, could be reduced to close to zero.
As for cost of an air quality monitoring program it is not at all that onerous for a well run liveaboard, resort, or dive shop. Quarterly testing by one of the four labs will cost between $300 and $400 dollars a year. This will monitor for less frequently occurring or problematic contaminants such as oil mist, CO2, water, and volatile hydrocarbons. The cost of a real-time compressor CO monitor from Analox is only $600 so the capital cost is nothing compared to other costs in running the business. Every two years a new sensor must be purchased for $150. So for about $500 a year a reliable testing program can be had which would reduce the CO exposure risk to zero.
If PADI and the other training agencies won't enforce their own guidelines then it will be up to individual divers to pressure their operators to follow the guidelines. If they won't then personal detection devices is the way to go.
