Coin batteries have a low voltage (1.5 V) and a diameter less than 12 mm to prevent any serious accident. Also, packaging has been designed specifically to prevent accidental ingestion. Panasonic coin batteries are thus relatively safe and serious accidents are very uncommon.
As zinc air hearing aid batteries operate differently than other batteries they have different characteristics. In winter, rooms may be drier, warmer or badly ventilated. These effects can disturb the performance of your batteries.