I just bought a new tank for CO2, as I'm looking to get into force carbonation. Almost everywhere I've called up in the DC area does tank exchanges and won't just fill up a tank you give them. I may have to exchange my tank if I have no other option, but seeing as it's brand new I'd prefer to hold onto it. Also, what's the verdict on non-food grade CO2, like from a place like Dick's Sporting Goods? Does that pose a real health hazard?