I drain 'em and leave 'em on my pool deck for a few days in the sun with the filler cap off to dry 'em out. But that's just me. Heck, why would they explode anyway? They're sealed and spend most of their lives with sloshing fuel in them sitting in the direct sunlight in a danged boat! I just stick 'em in a box, pad 'em up to keep from getting dented, and send 'em on their way. They usually run me about $15 to ship on average. No biggie.