I just remembered on from a friend of mine.
When winterizing a motorcycle (specifically, a race motorcycle), do Not drain the fuel tank (full of race gas) into the jar marked 'kerosene', and tell yourself that you don't need to relabel it. Of course you will remember that it's not kerosene.
When, three months later, you have pulled together a large brush pile that needs to be burned, and you've just doused it with the contents of the jar marked kerosene, FOR THE LOVE OF ALL YOU HOLD HOLY don't just shrug it off if you find yourself thinking "that kerosene smells a bit funny".
The resulting explosion rattled the windows of the ranch house, an acre and a half away. Which alerted his wife that something stupid had just happened.
My friend was not badly burned (as defined by 'requires hospitalization'). But he did raise the eyebrows of the ER triage nurse...