Use your CO analyzers

[Ron Lee]

Here is an interesting website:

Carbon Monoxide: A Fact Sheet

Here are a few of the CO symptoms versus concentration and exposure time. I am not a hyperbaric doctor so I will use reasonable assumptions. I will assume a 100 foot dive and that the surface CO PPM effect will be four times that at 100 feet. Example, a tank with 10 PPM CO at 100 feet depth will act the same as air with 40 PPM at the surface.

Here are the concentrations to discuss (assumed surface effects)

Concentration (parts per million) Symptoms
a. 35 No adverse effects within 8 hours.

b. 200 Mild headache after 2-3 hours of exposure.

c. 400 Headache and nausea after 1-2 hours.

d. 800 Headache, nausea and dizziness after 45 minutes; collapse after 2 hours.

e. 1000 Loss of consciousness after 1 hour.

Discussion:

a 35 PPM at 100 feet is the same as about 9 PPM CO at the surface. That is close to the 10 PPM offered as an allowable (not necessarily desirable) limit in another post. No effect so it would appear to be safe.

b. 200 PPM CO at depth is like 50 PPM on the surface. I would not like that but even if it happened, the 30 minute dive is only 25% of the lowest exposure where the symptom might occur. I would want to be much further from the bad point than 25% if it were a fatal symptom (coming up) but this is just a mild headache so it is not that bad. Still, a surface 50 PPM I would reject.

c. to e. These get progressively worse to the point of becoming life threatening but are so far beyond one limit of 10 PPM CO to be a mute point.

Other factors to consider are typical CO exposure at home; what CO PPM does a person exhale (smoker and none) and what is the Carboxyhemoglobin (COHb) Saturation of smokers.

ggunn, you are correct. The cave diver death is not a confirmed CO poisoning event from what I have read. If it were being investigated in the US, there would be appropriate analysis and the always possible "It is someone else's fault" could be a factor.

 

[Mossman]

Discussion:

a 35 PPM at 100 feet is the same as about 9 PPM CO at the surface. That is close to the 10 PPM offered as an allowable (not necessarily desirable) limit in another post. No effect so it would appear to be safe.

b. 200 PPM CO at depth is like 50 PPM on the surface. I would not like that but even if it happened, the 30 minute dive is only 25% of the lowest exposure where the symptom might occur. I would want to be much further from the bad point than 25% if it were a fatal symptom (coming up) but this is just a mild headache so it is not that bad. Still, a surface 50 PPM I would reject.

c. to e. These get progressively worse to the point of becoming life threatening but are so far beyond one limit of 10 PPM CO to be a mute point.

Other factors to consider are typical CO exposure at home; what CO PPM does a person exhale (smoker and none) and what is the Carboxyhemoglobin (COHb) Saturation of smokers.

ggunn, you are correct. The cave diver death is not a confirmed CO poisoning event from what I have read. If it were being investigated in the US, there would be appropriate analysis and the always possible "It is someone else's fault" could be a factor.

So what happens, then, when a CO analyzing diver rejects tanks for a mere 7 ppm. I don't believe we heard how the financial end of the transaction was worked out between the OP and his unnamed dive op. Does the dive op refund half the money if the diver refuses to do a second dive because of 7 ppm or 10 ppm or even 20 ppm, thereby eating costs in a very competitive and already financially precarious business, or does the analyzing diver proudly declare that he's still going to pay for the dives even though the air wasn't up to his standards?

Like I said before, I've never seen anyone analyze a tank for CO. So this is all news to me. What happens on the boat when a tank fails to pass muster?

All this theory is wonderful, but I'm curious about the practical side...

 

[DandyDon]

Yeah, Mossman is trolling. Anyone who talks diving 10 Nitrox tanks without checking is either careless or intionally confusing the discussion by excluding the rest of that statement.

Ron, your simple math is only part of the problem. There is a lot more to it than that or 10 ppm would not be the max in the US, which some consider too high. Of the countries that bother setting limits, many use 3 ppm.

The most obvious other issue is that CO binds with red blood cells inhibiting their ability to transport O2 to body parts. This is offset somewhat by the PPO2 on a dive until you ascend, when PPO2 drops but the CO stays bound. No, the 10 ppm max is a liberal one. If I find a tank over that, I don't go to the dive site so ignore the troll's suggestion that I might be sitting on a boat with the skipper while others dive.

Air is .2% CO. At what level in a tank ought we to refuse to dive?

Excuse me? .2 = 2/1000 = 2,000 ppm so I don't know what you're talking about? CO2 maybe, but Wikipedia suggest air contains 0.039% carbon dioxide so I don't know. Getting CO and CO2 confused is a common typo that causes misunderstandings, and moving a decimal point can be as well, but I'm just guessing. Your statement makes no sense...??

Is that diver a physician? A coroner? A medical examiner? Is he Quincy?

Don't misunderstand me; I am not saying that I know for a fact that the death wasn't from CO poisoning, or that CO contamination is never a problem in SCUBA tanks on Cozumel, only that the above anecdotal evidence does not establish a confirmed case of a death from CO poisoning. You are stating something as fact when it is in my view your willingness to accept the opinion of an inexpert witness as fact because he agrees with your agenda, backed up by your suspicion that "they" don't want you to know what really happened.

He was one of the dead man's best friends. Yeah, I think he got the facts right. If one of your loved ones died on one of your trips, I would not grill you for proof on COD.

 

[Mossman]

Yeah, Mossman is trolling. Anyone who talks diving 10 Nitrox tanks without checking is either careless or intionally confusing the discussion by excluding the rest of that statement.

Honestly, my preference is to check the tanks myself. That's what was ingrained in me when I took nitrox. I've actually averted a potential incident by analyzing tanks that turned out to be mislabeled, preventing my buddy from hitting the sand at the Spiegel Grove on 35% - we had picked up the custom blended tanks right when the shop was closing, so we couldn't analyze them there, but I had fortunately brought my own and checked them before we got on the boat the next day, the 35% and 29% labels were switched. Oops.

But my current dive op doesn't like to carry an analyzer on board, even when I've asked. And I don't want to shell out the bucks for a new analyzer (my old OMS seems to be obsolete). So what do I do? Switch dive ops, shell out the money and hassle for my own analyzer, or just dive the damn tanks and hope for the best? Well, being an optimistic sort of guy, I've lately opted for the latter. After all, two people before me swear they checked the numbers, the original mixer and the owner of the dive op. Should I call either of them a liar?

My first experience with not being able to check the mix was on the Okeanos Aggressor in Cocos. The panga drivers/tank fillers would hop on the pangas where the tanks remained, fill them, and write the mix on their hands. They would then tell you what your mix was so you could log it. Occasionally they would forget which number on their hand was yours, but hey, it was all good. Of course you could jump from the moving boat onto the moving panga yourself and analyze it, except that there was no time since they were already giving the dive briefing. Trust me. So I did.

Ye who have no faith...

BTW, if the limit is set at 10 ppm, you know that's conservative as all limits are. So if your tank comes up at 9 ppm and you sit out the dive, who pays?

---------- Post added March 7th, 2013 at 07:11 PM ----------

He was one of the dead man's best friends. Yeah, I think he got the facts right. If one of your loved ones died on one of your trips, I would not grill you for proof on COD.

So you would just take it on faith?

Besides, that guy was on a rebreather, correct? Aren't we talking apples and oranges? Even if it was CO poisoning, it could have been contaminated scrubber.

 

[Ron Lee]

From this source the COHb level of smokers is about five times that of non-smokers:

http://www.masimo.com/pdf/clinical/...boxyhemoglobin-levels-in-smokers-nov-2007.pdf


Source: Air Composition

• Carbon monoxide - CO - 0 to trace (ppm)

Info on exhaled CO. Note that smokers exhale 10-30 PPM CO

Carbon Monoxide Facts | Permisable levels of Carbon Monoxide

 

[DandyDon]

From this source the COHb level of smokers is about five times that of non-smokers:

http://www.masimo.com/pdf/clinical/...boxyhemoglobin-levels-in-smokers-nov-2007.pdf


Source: Air Composition

• Carbon monoxide - CO - 0 to trace (ppm)

Info on exhaled CO. Note that smokers exhale 10-30 PPM CO

Carbon Monoxide Facts | Permisable levels of Carbon Monoxide

I don't know how accurate that is, nor care really. I don't mean to be rude, it's just that the maximum legal limit for tank air in the US is 10 ppm, so I am not going to try to second guess that limit. I'd raise hell now more than before if I found any digits over 3 as the filler is supposed to provide clean tank air - so if I find real levels of that toxic contaminant, what else could it have that I cannot test for, and why am I expected to accept negligence...?

Up to 3 ppm, I'll accept that portable units have limits and my operator handling is amateurish.

 

[Ron Lee]

Ok it has been established that up to an including 10 PPM of CO is acceptable.

 

[DandyDon]

Ok it has been established that up to an including 10 PPM of CO is acceptable.

By US standards, so what's your point? Some divers won't dive more than 3, and the fill station is negligent when they allow any.

 

[Ron Lee]

By US standards, so what's your point? Some divers won't dive more than 3, and the fill station is negligent when they allow any.

Don, these threads on CO are full of fear fongering and assertions with no factual backup.

From missing divers may have been impacted by CO to a cave diver is who pronounced dead due to CO with no proof to when you get 4 PPM CO the tank could have all sort of contaminants, there is little substantive discussion.

This topic is quickly approaching the validity of man-caused global warming and eating eggs will kill you.

 

[Mike]

Mike, you called what mossman is spewing logic. This guy isn't using logic, he's being a troll. Feeding him keeps him coming back for more.

People are too quick to label those that disagree with them or present differences in view points as trolls. There are people in this world who don't follow the herd, aren't scared to state and stand by an unpopular opinion, or see issues from a more sophisticated or very different perspective, this doesn't make them trolls. This country was founded on individualist not the sheeples that are too prevelant now.