Alerting Devices

The days of fire alarm bells are well and truly gone for new installations, although bells and sirens may still be present in historical systems. For new installations, a specific standard “rising whoop” tone is now mandatory, with an interspersed verbal message (except for very small buildings). The voice message will typically be something like “Evacuate the building using the nearest fire exit”, and provides positive direction to building occupants. 

Although point-type sounders are available to produce this standard alerting signal, it is now most common for a central tone and voice generator/amplifier to be located at the fire alarm control panel, with a network of loudspeakers to reproduce the signal around the building. 

Alerting device power comes from the fire alarm’s standby battery, and is not reliant on building mains power, which may well fail during an emergency.

The alerting signals through a building must be identical. For modest additions to existing systems, it is permissible to retain the existing sound (siren, bell). Also on large sites where there is a uniform alerting signal, it is permissible for additional (new) systems to retain the same signal (even if it is, say, a bell sound), however a voice message must be provided on the new system.