With all of the regulations and technology meant to keep people safe it's often easy to lose track of the meanings behind terminology. For example, every building has to have a fire alarm system, but the difference between a Class A system and a Class B system is something very few people know.


When a fire alarm is sounded, whether through a smoke detector, heat panel, or a pull switch, certain things happen within the system. An alarm usually goes off in a central security area for the building, and the same alarm is sent to the fire department. Then any peripheral devices, such as sprinkler systems, which are connected to the sounding alarm, will be activated.

Class B

Class B is the more common of the two fire alarm systems, and it is the error in its design that led to Class A systems being designed. When a Class B system sounds, if there is any sort of short in the wiring system, then all of the peripheral systems are effectively lost. The alarm can communicate with the security office, but if there's a short from the alarm to the sprinkler, the connection from the sprinkler to a further device such as a red light, all of the other devices are unable to be accessed.

Class A

A Class A fire alarm system has a solution for the effectiveness problems found in a Class B alarm system. If a Class A system is activated, it takes the same steps as a Class B system would. However, a Class A system is built with redundant wiring systems. In a Class A system, there are two connections, one from the alarm down the wire, and from each individual device back to the alarm. This redundant wiring helps keep the system optimized, and makes sure that connectivity issues don't result in additional risk to persons or property.


A Class A fire alarm system is more expensive than a Class B system. This is due to the extra installation and heightened redundancy. However, the Class A system is safer, and leaves less to chance with regard to safety and fire prevention.


A Class A fire alarm system can be installed into most existing alarm system. All that's required is that the proper wiring and connections be run and installed. This is often the case during retrofitting, when reconstruction of an existing building leads to higher priced safety being installed.