Used mainly for outdoor barbecues, these containers hold compressed propane fuel filled from large gas containers often seen in gas stations looking like a large super-soaker device (the similarities abound, yet propane explodes much more violently, while a super-soaker just melts). Never, ever leave a propane tank in a campfire, this does not lead to a happy outcome. natural gas tanks can also be found in cars (known to mortally explode when rear-ended) and new clean air buses.