These signs are fire alarms. They must be acoustic signals although it is permitted to accompany them with a illuminated sign, such as a flashing light.
The purpose of fire alarms is to ensure that people in the workplace are alerted to any outbreak of fire well before it becomes life threatening. The warning sets in motion a planned routine for evacuating the premises.
Fire alarms must provide a coded signal which:
- has a sound level considerably higher than the ambient noise level;
- is easily recognisable and distinct from other acoustic signals and ambient noise; and
- is continuous for evacuation or is part of a two-stage evacuation system.
A two-stage system helps to avoid congestion along emergency escape routes by emitting a continuous signal where the danger is more imminent whilst an intermittent signal sounds elsewhere as a 'stand-by' for the continuous signal. Employers are advised to consult their local fire authority before installation of such a system.
For either a continuous or two-stage alarm, the warning signal for evacuation can be supplemented by use of a public address system to give clear and concise instructions.