Direct answer
The building’s emergency plan defines the signal
In many simple workplaces, a continuous bell or sounder means everyone should leave by the nearest safe exit. More complex premises may use alert, evacuation, staff-alarm or voice messages to manage phased movement.
Do not wait for smoke or a second signal unless the premises plan explicitly requires an alert stage and you are trained for it. Visitors and contractors also need understandable instructions.
Different strategies
One sound pattern cannot describe every premises
Care premises, theatres, high-rise buildings, shopping centres, hotels and sites with hazardous processes may use staff intervention, progressive movement or phased evacuation. The alarm cause-and-effect should match the fire strategy and FRA.
Where the warning is shared between tenants, landlord and occupiers must coordinate testing, signals and out-of-hours response.
Make it understandable
Training and fire action notices translate sound into action
Fire action notices should state what people do when the alarm sounds, how to call 999, where to assemble and any building-specific arrangements. Training and drills should confirm that signals are audible, recognisable and acted on.
Visual alarms, vibrating devices, paging or staff assistance may be required for people who cannot rely on an audible signal.
Unexpected activation
Treat an unexplained alarm as real
Leave by the nearest safe route and do not re-enter until authorised under the premises plan. Staff should not silence or reset an alarm simply because a cause is not immediately visible.
Afterwards, record the activation and investigate false-alarm or system issues with competent help. Repeated unwanted alarms can erode response and require an FRA review.