While getting rid of an old bookcase, we found what appears to be black mold under it. It was not damp at all, but looks like it had time to live in the carpet area and on the base of the bookshelf for a while as the area is completely covered. This is the room that (when I was buff and strong), did my daily workouts and weight lifting.... bouncing around, doing interval training and then getting down on that rug to do pushups.
I was probably kicking up dried mold spores all around.