I got this in an email today, haven't run it through snoopes or anything like that, thought I'd post it here. Just in case.
Hey guys. I was at a meth training/workshop yesterday and there was a lot of great new information presented. I wanted to let you all know about one thing that I was not aware of. Meth cooks are getting the propane tanks from the exchanges at Wal-Mart, Kroger, etc. and emptying them of the propane. Then, they are filling them with anhydrous ammonia (which they now have a recipe for by the way). After they are finished with them, they return them to the store. They are then refilled with propane and sent back for you and me to buy. Anhydrous ammonia is very corrosive and weakens the structure of the tank. It can be very dangerous when mixed with propane and hooked up to our grills, etc.
According to our presenter, you should inspect the propane tank for any blue or greenish residue around the valve areas. If it is present, refuse to purchase that one.
Just felt a duty to warn. Have a great weekend.
"You miss 100% of the shots you don't take."-Wayne Gretzky