They are readily used in brewing for carbonating and serving tap beer. I think they're okay, but if you're worried you can buy a brand new canister and only ref

They are readily used in brewing for carbonating and serving tap beer. I think they're okay, but if you're worried you can buy a brand new canister and only refill with food grade CO2. You can see this for a bit of information https://cooking.stackexchange.com/questions/43655/is-there-such-a-thing-as-food-grade-co2 https://cooking.stackexchange.com/questions/43655/is-there-s...