So turns out 0000 steel wool is both conductive, and flammable. I had a few 9 volts sitting in a shelf space with a bunch of bass related tools and such. I shifted some stuff around grabbing cables and saw some sparks. Then it started straight up catching on fire when I picked it up. My first thought was to blow it out, that didn't go well. Threw it into the sink before anything else caught. Kinda freaky since all the stuff had been sitting there for months within inches of where this happened. Even if I hadn't burned the house down this was directly over most of my nicest instruments! It reminded me of an incident years ago when the two 9 volts in my pocket lined up just right and created a REALLY warm spot in my pocket. Gotta be careful with those 9 volts!