Chemicals  Don't use barrels that have had some kind of chemical stored in them. It won't burn out for a long time and will surely make your food taste bad, and might just make you sick. Rust  I got in a hurry to build this smoker when I first started. I was in such a hurry that I got some barrels that had some major rust on them and thought they would do. Don't do this. I spent about 3 hours sandblasting one of them and then stopped. Wasted the three hours. I then did the right thing and made a burn barrel out it. I then when back on the hunt for some newer barrels that had contained some food grade product.