As per the thread title really. I just brought home about 10 mini canisters that someone had dumped in the stream where I walk the dog. They look like air rifle or soft air types but I've never used them so could be something else. I know they're steel because my magnet on a stick picked them out of the water. They seem to be empty but the valves are rusty so I dont know if I can test them. What do people do with dead ones? (Dont say chuck them in a stream )