Brules
Contributor
Like a boss! You guys are doing it right!
Do get a co analyzer or not?
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Like a boss! You guys are doing it right!
suprane
Contributor
markmantei
Contributor
Dave, your devotion to doing the "right" thing is admirable, and I do not limit that the CO situation being discussed in this particular thread.
That is good news Dave! I suggest that you announce it in a new thread so that more people can see it. At the least, you should update your website to include this information.
diverkun
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Permissible limits?
aside from the whole question of individual testing, what do you do with the results?
I am having a hard time getting a clean answer on what permissible CO limits are for diving. A quick wiki search shows OSHA long term exposure limits at 50 ppm, DAN indicates that ambient air can be 10 ppm (Alert Diver cites CGA, ANSI). Several posters note concern over 15-20 ppm readings.
What reading would cause you to reject a fill as an unacceptably high CO Level? 10 ppm? 20 ppm? higher?
Do you have different threshholds for repetative dives or different depths?
aside from the whole question of individual testing, what do you do with the results?
I am having a hard time getting a clean answer on what permissible CO limits are for diving. A quick wiki search shows OSHA long term exposure limits at 50 ppm, DAN indicates that ambient air can be 10 ppm (Alert Diver cites CGA, ANSI). Several posters note concern over 15-20 ppm readings.
What reading would cause you to reject a fill as an unacceptably high CO Level? 10 ppm? 20 ppm? higher?
Do you have different threshholds for repetative dives or different depths?
markmantei
Contributor
I believe Canada's max permissible level is 5ppm, US is 10ppm. At 5ppm I would definitly be reducing my planned depth and questioning doing the dive with that air at all, can't say what I would do for sure. At 10ppm I would not use the tank for snorkeling.
Those values are absolutes. The issue is partial pressure, just like 02 limits when diving nitrox. I would not adjust those values for repetitive dives. I would consider planned max depth when deciding however.
suprane
Contributor
markmantei gave a pretty good brief description. (I was hoping someone would as I tend to get way too verbose!)
There are no absolutes that have been established, as the certifying agencies (CGA; Compressed Gas Association in the US) in large part have no way of predicting to what depth you will be diving. And as markmantei eluded to, your exposure increases as you go deeper. So if your gas tests, say, 10 ppm at the surface, then that is your exposure at 1 ATA (Atmospheres Absolute). If you now descend to 132 ft (40 meters) You are now at 5 ATA. Now your exposure is essentially 5 times greater than at the surface! You are now breathing the equivalent of 50 ppm! This is why when DandyDon and I were confronted with tanks testing 17 ppm with a dive scheduled to Devil's Throat (depth 130 to 135 ft at the least!) we said "no"! Our exposure would have been the same as sucking 85 ppm CO!! We were not about to do that! We settled on a shallow dive (50 or 60 ft. as I recall). And we were much more comfortable with that, even though we were still very disturbed that the tanks were that high to begin with!
So, at this point you sort of have to decide for yourself what your comfort level is based on the starting quantity of CO and your planned depth and time of dive. Personally, I would not do a dive to 5 ATA with anything greater than 5 or 6 ppm, whereas, at 40 or 50 ft I might be comfortable with perhaps as high as 10 ppm.
Realistically it is my understanding that compressed SCUBA air should actually test out at close to 0 ppm as there are catalytic CO "scrubbers" in the filter system that should remove virtually all of it..... Please, if there is someone that knows more about compressors than I do, feel free to jump in at this point!
My wife, also a diver, bought me an Analox CO monitor for Christmas. I will be using it this spring when I begin diving again and when I go to Cozumel in July. Depending on who I dive with, I may have the opportunity to test tanks before leaving the caleta and therefore can deal with it then, I guess by switching around tanks so I don't get poisoned. If I dive with an op that has already loaded the boat with tanks, and I find one or more or all of the tanks are contaminated, what then? Nobody dives? The op calls the dive until they get new tanks? I dive mine and tell the other folks, "good luck. Take your chances"?
I would think anyone properly trained would agree that it is the diver's responsibility to assure safe diving equipment for themselves and taking measures to do so. I believe the underlying question is what to do about it, which is to miss dives, enjoyment, revenue, etc. While the answer is obvious, life trumps fun, no one wants to screw it up for everyone else.
I would think anyone properly trained would agree that it is the diver's responsibility to assure safe diving equipment for themselves and taking measures to do so. I believe the underlying question is what to do about it, which is to miss dives, enjoyment, revenue, etc. While the answer is obvious, life trumps fun, no one wants to screw it up for everyone else.
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