When I disposed of an underground fuel oil tank (for oil burning furnace) I read where the disposal company was supposed to fill the tank with carbon dioxide before hauling it away. However, never saw the driver do anything except tie it down well and hit the highway. Cost me a pretty penny, too.
I have worked on a couple of tanks, even filled w/ water, the area left on top to weld on have popped(exploded) a little . Always look away w/ protection on before hitting it w/ flame or what ever.
