How Much CO is divable
- Thread starter BertStevens
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It is nice to see many others discussing the risk that the agencies and DAN avoided for years. There were times I felt like Dandy Don Quixote.
Yeah, that sounds nice but you can't seriously test that accurately in the field. Measuring in parts per million even with a well calibrated tank tester is subject to rounding and operator handling. A 1 or 2 could be a false positive.
Do you test every tank or just when suspicious for some reason. I've see a number of 3s, 5s, and some 7s - complained, but dived while trying to maintain increased awareness of possible issues. It does help to carry a 19 cf pony that tested zero for backup. I wouldn't suggest anyone else dive a tank that tests over 3, but I do a lot of things I wouldn't suggest to others.
Breathing 10 ppm at the back of a boat is at one atmosphere so it won't hurt you. Filling a tank with that level and diving it to 4 or 5 atmospheres greatly increases PPCO exposure, plus the cumulative effects, and then the zinger of ascending and reducing PPO.
I do test every one of my tanks. The DiveNav unit makes it stupid simple. It's so convenient there's no valid excuse not to test.
I probably should have clarified. I'm ok with what could be considered an ambient reading or a calibration error. So realistically 1ppm, but anything more than that, I'm not diving those tanks. I make sure to test them before they go on the boat or in the truck. No one has ever tried to tell me to just dive them anyway. And with an inflation bottle first stage and the 1 lpm adapter that comes with it, ops are generally happy to have me test several tanks if required. They're not losing enough gas to make a difference, and it's doing them a service.
I probably should have clarified. I'm ok with what could be considered an ambient reading or a calibration error. So realistically 1ppm, but anything more than that, I'm not diving those tanks. I make sure to test them before they go on the boat or in the truck. No one has ever tried to tell me to just dive them anyway. And with an inflation bottle first stage and the 1 lpm adapter that comes with it, ops are generally happy to have me test several tanks if required. They're not losing enough gas to make a difference, and it's doing them a service.
Just to expand on the comment about CO (carbon monoxide) bonding to haemoglobin.
The section from the US Navy manual is very good.
Just to repeat the issue.
Carbon Monoxide binds to haemoglobin 300 times more powerfully than Oxygen. If you breathe contaminated gas, then the majority of the haemoglobin will change to carbonoxyhaemoglobin, once this happens the haemoglobin can no longer carry oxygen.
We should all understand that it is the haemoglobin that normally carries the oxygen around the blood as oxyhaemoglobin. Once this stops happening cells start to die!
The biggest issue is that even if the diver is removed from the contaminated gas, the damage is already done. The preferred method for treating Carbon Monoxide poisoning is hyperbaric oxygen. If hyperbaric treatment is unavailable, then it’s 100% oxygen on the surface, if 100% oxygen is not available, then the richest Nitrox you have, after that air!
As others have said, is the partial pressure of the Carbon Monoxide that is the danger in diving. As a rough example.
Breathing 0.1% CO on the surface (1000 parts per million) an individual would suffer severe symptoms of CO poisoning in about an hour.
If a diver breathed the same mix and attempted to descend to 40m (120ft), they would probably be dead before they reached the bottom.
Gareth
The section from the US Navy manual is very good.
Just to repeat the issue.
Carbon Monoxide binds to haemoglobin 300 times more powerfully than Oxygen. If you breathe contaminated gas, then the majority of the haemoglobin will change to carbonoxyhaemoglobin, once this happens the haemoglobin can no longer carry oxygen.
We should all understand that it is the haemoglobin that normally carries the oxygen around the blood as oxyhaemoglobin. Once this stops happening cells start to die!
The biggest issue is that even if the diver is removed from the contaminated gas, the damage is already done. The preferred method for treating Carbon Monoxide poisoning is hyperbaric oxygen. If hyperbaric treatment is unavailable, then it’s 100% oxygen on the surface, if 100% oxygen is not available, then the richest Nitrox you have, after that air!
As others have said, is the partial pressure of the Carbon Monoxide that is the danger in diving. As a rough example.
Breathing 0.1% CO on the surface (1000 parts per million) an individual would suffer severe symptoms of CO poisoning in about an hour.
If a diver breathed the same mix and attempted to descend to 40m (120ft), they would probably be dead before they reached the bottom.
Gareth
I can get 2ppm on a normal exhalation (and I don't smoke). Anymore than that and I'm not diving.
KDAD
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According to a paper from Ryter and Choi, the exhaled CO value of non-smokers could be about 3 ppm while the mean value of exhaled CO for smokers was 17 ppm.
Additionally, cootwo includes a temperature sensor and a temperature compensation algorithm.
kafkaland
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I recently had a tank testing at 4ppm at the dive shop where I was renting it from. I rejected it and got one that was fine instead. And they did let their fill station know.
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