evacuation exit; escape hatch
A door or opening specifically designed for evacuation in emergencies, such as in buildings, ships, or aircraft.
In case of fire, please exit through the evacuation door.
This building is equipped with multiple evacuation exits.
避難口 is a general term for any evacuation exit, while 非常口 specifically denotes an officially marked emergency exit with the standard green sign.
Compound of 避難 (ひなん, 'evacuation') and 口 (ぐち, 'opening' or 'exit').