The Five-Minute Project in the November 2006 issue, “The Nine-Volt Safe,” involved sliding off the top of a 9-volt battery. Although experts advised us that it is not normally dangerous, and we tried the project ourselves without incident, it has come to our attention that in rare instances, the cells inside the battery can “vent” or rupture, potentially exposing the handler to the chemicals inside. Given even the small chance of injury related to this project, we advise you not to undertake it.