Hi Wookie,I don't understand how you get 80 PPM in one tank and none of the others. I'm not questioning you, not at all. It's not like a slug of CO gets released into a compressor and then goes away. CO in a compressor comes from an engine nearby but the hopcalite in the filter tower should take care of that in small doses. The other way is to burn the compressor oil, but again, that's a slow process, and should contaminate more than one tank.
Someone needs to spend a fortune studying the phenomena.
After draining the tank it was found to have almost 6 inches of seawater in the steel tank that had been sitting for a couple of months. The tank was completely rusted and I put down the formation of the CO to the corrosion process that also took place on the carbon content of the steel. The tank had probably been drained and then swum in from the dive boat where it sucked in water after hitting the colder water. There was probably little oxygen left based on the degree of rusting.
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