We are just starting into kegging and need to get a CO2 cylinder filled. Does anyone know if there is a difference between industrial grade CO2 and food/beverage grade CO2? Did some internet searching – most homebrewers think that CO2 is CO2 and buy theirs from wherever it is cheapest, but a few maintain that you should only use a food grade CO2. Still others say that it is the cleanliness of the inside of the tanks that is most important (and just how would I check that?!). Does anyone have any thoughts on this?