Fire hazard in your junk drawer.

I knew about the ability for a 9v to start a fire, but it never dawned on me that multiple 9v batteries would ultimately get put in series, laying on their sides against something metal (like the wall of a stainless toolbox, or other tools, like a carpenter's knife, staple gun or a piece of hardware) and could take quite a bit of time to generate a sufficient amount of heat to set something off, meaning just an hour or so after rifling through a drawer or container, it could blaze up, unattended.