What is the meaning of alarm, as in a three-alarm fire? Obviously, the more alarms there are, the more serious the fire, but what does an alarm measure?
An alarm is a warning, signal, or call to action. It originated as a call to arms — “All’arme!” (To arms!) in Old Italian. As used by fire departments, the signal is preceded by a number, which alerts the dispatcher to the magnitude of the fire and the response required. The numbers represent preestablished assignments of apparatus and manpower and allow the dispatcher to know instantly how much equipment and how many firefighters will be needed to do the job. The higher the number is, the more of each will be required.