Do You Analyze Your Gas for CO?

[Webmaster]

I certainly do now.

Got some when we were filling off a gasoline compressor a couple of years ago diving in Jasper. I made it out of the cave, but I didn't think I was going to make it up the hill to the truck without puking and/or passing out. And getting out of the tanks at the waters edge I was about half worried I was going to pass out and drown in 6" of water.

It didn't really hit me until the way out. Pounding headache at first then cramps, weakness, confusion, nausea.

I didn't have an analyzer then, but we checked it with someone else's after the dive. I think it only read like 3ppm or less, that may be a bit fuzzy, but I remember that it wasn't very much. That may be why it took most of the dive to manifest symptoms.

[RN]

Must have been more than 3ppm. That's the acceptable quantity for oxygen compatible air. 10ppm is the acceptable quantity for grade E scuba air. 300ppm goes more along with your symptoms.

Concentration.........Symptoms
35 ppm (0.0035%).....Headache and dizziness within six to eight hours of constant exposure
100 ppm (0.01%).......Slight headache in two to three hours
200 ppm (0.02%).......Slight headache within two to three hours; loss of judgment
400 ppm (0.04%).......Frontal headache within one to two hours
800 ppm (0.08%).......Dizziness, nausea, and convulsions within 45 min; insensible within 2 hours
1,600 ppm (0.16%)....Headache, tachycardia, dizziness, and nausea within 20 min; death in less than 2 hours
3,200 ppm (0.32%)....Headache, dizziness and nausea in five to ten minutes. Death within 30 minutes.
6,400 ppm (0.64%)....Headache and dizziness in one to two minutes. Convulsions, respiratory arrest, and death in less than 20 minutes.
12,800 ppm (1.28%)..Unconsciousness after 2–3 breaths. Death in less than three minutes.

[Webmaster]

And that may illustrate the need for somewhat frequent calibration.

Or I may just be remembering it wrong, I wasn't exactly the most clear headed at the time.

[FW]

Wouldn't the effects be greater at depth?

[DGraham]

Wouldn't the effects be greater at depth?

I would think that if you started out with 3PPM (.0003 %) and were diving to 90 mtrs you would have a final PPCO of somewhere around 30PPM (.0030 %); which according to the table from Rob would give you a slight headache and dizziness after 8 hours of constant exposure.

10PPM would end at 100PPM and would give you the headache after 2-3 hours of exposure. This sounds like something we could experience, but at 90mtrs, not 30mtrs like most caves. 10PPM in 30 mtrs would be 40PPM and that is acceptable except for very long exposures.

My personal line is 0. If there is any showing, then there is an issue somewhere and it needs to be figured out and corrected. I too analyze all of my bottles, but we make CO monitors here at work and they don't cost me much of anything

[RN]

Wouldn't the effects be greater at depth?

Yes, but the 3ppm and 10ppm are based on exposure to recreational limits of 130 fsw. 10ppm is acceptable risk to a max depth of 130 fsw using an AL80. At least it is by the industry standards.

[kwinter]

I would think that if you started out with 3PPM (.0003 %) and were diving to 90 mtrs you would have a final PPCO of somewhere around 30PPM (.0030 %); which according to the table from Rob would give you a slight headache and dizziness after 8 hours of constant exposure.

10PPM would end at 100PPM and would give you the headache after 2-3 hours of exposure. This sounds like something we could experience, but at 90mtrs, not 30mtrs like most caves. 10PPM in 30 mtrs would be 40PPM and that is acceptable except for very long exposures.

Not really. It's all about the partial pressure. The fraction doesn't change. If it's 3 ppm at the surface it is still 3 ppm at 90 meters. Just like air is 21% oxygen no matter how deep you go. But the pCO would of course be 10 times greater at 90m, so the effect would be like 30 ppm at the surface.

Just setting the record straight.


iPhone. iTypo. iApologize.

[DGraham]

Thanks for the correction. You said it much clearer than I did.

Now, the question is does the effects equal to 30ppm at depth compare to the effects of 30ppm at the surface? Or are the effects amplified?

[RN]

Basically what it comes down to is if you have more than a 10ppm reading on your analyzer then do not breathe that gas.

[kwinter]

There seems to be a very wide range of opinion about safety levels for CO. The instructions with my Analox analyzer quote a British source and say that 3 ppm is the max safe level for air dives to 50 m. That's 6 ATA, or the equivalent of 18 ppm at the surface. But the Consumer Product Safety Commission responsible for things like heaters and furnaces says that a level under 70 ppm is tolerated well and should not be a problem. It isn't until well over 200 ppm that they even say headache is common and into the thousands before death is a serious risk.


iPhone. iTypo. iApologize.