I bought a CO2 bath from Steve at Carbogenetics 2 years ago. Have the whole set up already but haven't really used it. It was hard to use by myself as you need a buddy to be there in case of an emergency situation. Last time I was in touch with Steve he's developed a space suit like contraption that's more practical and he says he was testing it out with a lab at Stanford. I'll have to check with him on his progress.I think the tank is the only reliable way unless you live by a spring known to be rich in carbonic acid and can bathe in it....