A fire alarm is the bell or siren that warns a building of fire. Set off the fire alarm.
Most are triggered by smoke rather than heat, since smoke arrives first. A fire alarm that goes off often is ignored, which is the whole danger of a faulty one.
1nounfire alarmThe bell or siren that warns a building of fire.
“The fire alarm went off at four in the morning three nights running.”
fire alarm is a device.
Fire plus alarm, from Italian all'arme, to arms.
From fire + alarm.
Etymology from Wiktionary, CC BY-SA
Practised in Emergency & Rescue