A fire alarm that goes off when there is no fire is not harmless. Every false alarm costs lost production, trains occupants to hesitate, and may bring an appliance that is then not available for a real fire. Several Fire and Rescue Services now charge for repeat attendances to automatic fire alarms, and some no longer attend unconfirmed signals from certain premises.
Common causes
| Cause | Typical fix |
|---|---|
| Cooking fumes and steam near smoke detectors | Change to heat or multi-sensor detectors; relocate; add local extract |
| Dust from building works | Detector covers and temporary disablement with a permit-to-work; clean detectors afterwards |
| Aerosols, e-cigarettes and hair straighteners in accommodation | Multi-sensor detectors; occupant information; detector positioning |
| Insects and dirt in ageing detectors | Detector replacement at end of life (typically ten years); regular cleaning |
| Malicious or accidental call point operation | Protective covers to BS 5839-1; relocation; CCTV where persistent |
| Faulty or incompatible equipment | Investigation of the event log; replacement of failing devices |
Finding the cause
Addressable panels hold an event log showing which device activated and when. Patterns emerge quickly: the same detector at the same time every weekday is a kettle or a shower, not a fault. We review the log at every service, and BS 5839-1 requires an annual review of the false alarm record with recommendations.
Design measures
- Multi-sensor detectors that need both smoke and heat criteria before alarming.
- Staff alarm or investigation delays in staffed premises, giving trained staff time to check before general evacuation.
- Coincidence detection (two devices) before signalling to the ARC.
- Time-of-day sensitivity changes in areas with predictable activity.
- Cause-and-effect changes so a single detector does not trigger a full building evacuation where the fire strategy allows.
Do not simply disable the detector. An isolated device is an uncovered area and a non-conformance. Fix the cause or change the detector type, and record every disablement in the logbook with its reason and duration.