Hearing Aid Batteries are Zinc-air, button-shaped disposable batteries. They are air-activated and factory-sealed which remain inactive until removed. Once the sticker on the battery is removed the oxygen will interact with the zinc and it will turn on. As long as the Battery is in contact with the oxygen, it will be in the active state until the power is drained. 

Hearing Aid batteries are highly efficient in nature. They can be stored for a longer period of time when not in use. Traditionally hearing aid batteries were produced using traces of mercury to assist with conductivity and stabilizing the internal components, but mercury is no longer used in hearing aid batteries while Zinc-Air Batteries are more efficient and Cost Friendly.