Even carbon zinc and alkaline batts can be dangerous in direct short mode. I've told the story here about one of my fellow tech reps tossing a new 9v voltmeter battery into his tool bag after changing one out of a pack of two. We were servicing some computer room equipment at the time. I smelled something and turned around to see smoke coming out of his tool bag. It was the fresh 9v battery that had shorted when pressed against a tool. He grabbed it and quickly dropped it after creating an inch long blister on his thumb and finger! If we had walked out of the room for a few minutes, I'm confident that a tool bag fire could have resulted. All from a tiny 9v alkaline cell. They should be shipped with the little plastic snap on protectors.