A seven-alarm fire is one in which the on-scene fire commander has asked for help seven times. Fires that require more than one truck or one company's response are known as multi-alarm fires.
Each fire house has a typical format that includes a predetermined response for the initial fire call, known as the first alarm. There are various such resources sent to a fire:
- Fire trucks
- Fire personnel
- Additional emergency personnel
The fire chief or commander at the scene of a fire determines when additional resources are needed. For example, the commander might call for a second alarm, which is also a predetermined response. The number of alarms may refer to the number of individual fire houses or companies working on the emergency, or it may refer to the number of trucks and resources.