Most battery systems generate some gas internally
whether in use or on the shelf. An exception is the mercury/cadmium system,
which does not. These gases must be allowed to escape to avoid leakage or cell
rupture. Typical designs incorporate some sort of venting mechanism.
Carbon/zinc cells typically use porous carbon electrodes to allow venting.
Alkaline cells usually have a vent built into the cell seal that is designed
to rupture before cell disassembly. The cell is usually ruined once this vent
activates. Some electrolyte leakage may be experienced as