A 9 volt battery is a fire hazard because the positive and negative posts are on top, right next to one another. If the ends come in contact with anything metal i.e. aluminum foil, steel wool, paper clip, other batteries, etc. this will create the object to heat up and ignite a fire. To store, keep in original packaging or keep ends covered. For disposal, make sure that the positive and negative posts are safely wrapped in electrical tape.