noun
A device that detects fire and sounds an alarm. Often found in buildings and public facilities.
火災報知機が鳴ったら、すぐに避難してください。
If the fire alarm goes off, please evacuate immediately.
火災警報器 is a broader term for fire alarm equipment, while 火災報知機 specifically refers to the notification device.
Compound of 火災 (fire disaster), 報知 (notification), and 機 (device).