Nonsense! My old buddy "Three Fingers" Donovan told me it's perfectly safe and you don't need to empty the cans before you start welding.

There was a feller local to my area that got himself involved in stolen credit cards. He had welded himself together something that could only be called a vat in the bed of his truck that could hold 300+ gallons. They caught him at the station when he came back for the fourth time.