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I just picked up a Carbon Analyzer from the UK and it states that a tank containing more then 3 ppm isn't safe &
my friends Carbon Analyzer from the U.S. states that a tank containing more then 10 ppm isn't safe. So the question is to any Tek Diver out there what is max amount of carbon in a tank ______ppm that is safe to dive at a depth of 130ft on a air fill ????? If the U.S. is saying 10 parts per million is safe then we know that the U.K.is playing it extremely safe.. But I have heard of guys diving with tanks containing 15 ppm... So can anyone explain the big gap from the U.S. & UK ??? Some country's say 3ppm -10ppm & 15ppm so who is right ??? I just want to know the max amount of carbon a tank can contain before one passes out!! Thanks Danny
Well, Danny, Carbon Dioxide is considered safe for breathing air at 1000 ppm in the United States, but only at 500 ppm in Canada. I would suggest that powdered carbon is not good to breath at any level, and carbon tetrachloride the same. Carbon Monoxide limits are set at 10 ppm in the United States, so you're safe up to 10 ppm in the United States, but you'd likely die with that much Carbon Monoxide in the UK.
The real answer is that everyone's physiology is different, and we all process CO differently. Even if the specification is 10 ppm in the USA, I'd find a fill station that tests at less than 0.3 ppm, the minimum dectable amount.
In tests with human volunteers breathing 50 ppm carbon monoxide (a concentration that produces 27 percent carboxyhemoglobin after an exposure of 2 hours), there was a significant decrease in time to onset of exercise-induced angina[Gosselin 1984]. Carbon monoxide can be transported across the placental barrier, and exposure in utero constitutes a special risk to the fetus. Infants and young children are generally believed to be more susceptible to carbon monoxide than adults.
Healthy young men exposed to carbon monoxide at a concentration of 44 ppm for a prolonged period suffered no adverse health effects [ACGIH 1986]. Men exposed to 50 ppm for several days without relief complained of headaches, but exposure to 40 ppm for 60 days was without effect [ACGIH 1986].
Most CO monitors will alert on 10 parts per million. However, the
EXPOSURE LIMITS
* OSHA PEL
The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for carbon monoxide is 50 parts per million (ppm) parts of air (55 milligrams per cubic meter (mg/m(3))) as an 8-hour time-weighted average (TWA) concentration [29 CFR Table Z-1].
* NIOSH REL
The National Institute for Occupational Safety and Health (NIOSH) has established a recommended exposure limit (REL) for carbon monoxide of 35 ppm (40 mg/m(3)) as an 8-hour TWA and 200 ppm (229 mg/m(3)) as a ceiling [NIOSH 1992].
* ACGIH TLV
The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned carbon monoxide a threshold limit value (TLV) of 25 ppm (29 mg/m(3)) as a TWA for a normal 8-hour workday and a 40-hour workweek [ACGIH 1994, p. 15].
* Rationale for Limits
The NIOSH limit is based on the risk of cardiovascular effects [NIOSH
The ACGIH limit is based on the risk of elevated carboxyhemoglobin levels [ACGIH 1991, p. 229].
GREAT THREAD - I think Dandy Don should chime in soon - he is kind of the unofficial CO guru on here. I just ordered a CO tester and Ive been trying to figure out where to "draw the line". Im thinking 5-7ppm will be my limit. I would love to hear other opinions as Im not entirely sure yet.
Good comparisons on carbon there Wookie. Yeah, CO or Carbon Monoxide is the common issue as too many compressors don't monitor or test, yet some allow too much in tanks at times - and then discussions here so often include typos about CO2 which is not a significant risk. Funny how atoms combine in various ways that can affect us differently.
Most CO monitors will alert on 10 parts per million.
I'm thinking that you meant that totally different that you said it. CO monitors can vary a lot, home CO monitors don't alert until they sense a much higher number for a pretty long period of time, and I'm sure there are many others. Analox Clear inline compressor monitors can be set at different levels. Dave said he is having his new compressors installed with two each, one to sound at 3 pppm and the other to automatically cut-off the compressor at 10 ppm.
CO analyzers or testers are a different issue, and those units also vary a lot, some having different alarm levels. So, your remark actually fails in any consideration I can think of, but maybe you meant it different. And as I noted in our Speed vs Fuel Efficiency, we know we can't tell an engineer anything. :laughing:
I should find a good Dilbert cartoon to inset here, huh?
GREAT THREAD - I think Dandy Don should chime in soon - he is kind of the unofficial CO guru on here. I just ordered a CO tester and Ive been trying to figure out where to "draw the line". Im thinking 5-7ppm will be my limit. I would love to hear other opinions as Im not entirely sure yet.
I am not at all any sort of guru, you know - but thanks for the support. I'm more of a fumbling diver who has survived a lot of screw ups on over 400 descents, plus picked up knowledge here and there on the problem that does exist with too little being done to prevent CO in our tanks and how dangerous that can possibly be in some case resulting in negligence deaths. My goal is to alert other recreational & tech divers who are unaware of the problem, what we can pressure the operators to do to prevent it - and it doesn't take much, what we must do ourselves to prevent hits from unexpected CO toxicity, plus just maybe pressure Padi & DAN to take action beyond lip service. :silly: I have received a lot of help from some real authorities, but I'm still not one.
At what level do you refuse to breathe a tank? Pick a number between 3 & 15 - ppm, not % - then stick to it. Of the countries that do have regs, enforced or not, that's the range. Your call. For me now, I start complaining when I see 3 and getting off of the boat at 10. Some are less accepting of 3 to 5 ppm readings.
I know some more accomplished divers than I who will not accept anything over 3 ppm, and we shouldn't have to - but we are really still learning with newly available technology, so it's hard to say what a reasonable limit it. What CO does to us on descent with increasing partial pressures partially offset with increase PPO, how much it binds to our blood to harm us more on ascent when PPO drops but the CO effect doesn't, and more is still being discovered actually - and again even DAN is not doing much there. It's even difficult to learn what the CO levels actually were in tanks that did killed or injure divers as local testing possibilities has often been lacking and results very often kept quiet as bad for business. We are trying to be more careful, as well as learn how careful we need to be.
One would think that Analox would give you a thorough answer when asking them the same question, but they didn't. Disappointing because they state after numerous CO Test for their new analyzer the safest level of CO is 3ppm. Great please explain your findings, tell us what happen when the levels of CO went up with your divers etc. Thanks everyone for your help. See you at the bottom
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