False alarms: prevent and handle

The London Fire Brigade attended over 40,000 false alarm signals in 2024. Each one costs the brigade, costs your tenants, and erodes the trust that makes the next real alarm get the right response. Reducing false alarms is part of a competent fire alarm strategy.

What counts as a false alarm

BS 5839-1 categorises false alarms in four ways:

• Unwanted alarms caused by working environments — cooking fumes, dust, steam, aerosols, contractor activity
• Equipment false alarms caused by faulty devices, dirty sensors, or insects in detectors
• Malicious alarms — call points operated deliberately when there is no fire
• System false alarms caused by panel faults, wiring faults, or commissioning errors

The four are diagnosed differently. Conflating them — "we get a lot of false alarms" — doesn't help fix any of them.

How to reduce them: site-side

The actions that consistently reduce false alarms:

• Cook in the kitchen, not under the smoke detector. If kitchen activity is producing alarms, the detector position is wrong. Heat detectors belong in kitchens; smoke detectors do not.
• Brief contractors before they start. Use the dust covers we provide, and have a positive system isolation procedure that's documented and known to the contractor.
• Move call points away from corridors that get used as shortcuts. Mounting height and recessed positioning helps.
• Replace dirty detectors. The chamber gets dust and insects over years; the device's sensitivity drifts upwards. Replace, don't try to recalibrate.

How to reduce them: system-side

What we do at the system level:

• Verify mode on detectors in problem areas — the panel waits for two activations or a sustained signal before generating an alarm.
• Multi-sensor detectors that combine smoke, heat, and sometimes CO, requiring the combination before triggering. Significantly lower false alarm rates than smoke alone in mixed environments.
• Time delays and investigation periods in commercial premises, allowing a brief window to investigate before the system actuates evacuation signals — within the parameters BS 5839-1 allows.
• Cause-and-effect tuning — pre-alarm and warning states that flag a problem area without going to full evacuation.

These are all design and commissioning choices. Retrofitting them mid-life requires a competent person.

When a false alarm happens

When the panel shows fire and you have determined it is false:

1. Don't reset before the brigade arrives if they have been called or are on the way. The investigators want to see which device triggered.
2. Log it before resetting. Time, date, zone, device address, suspected cause.
3. Investigate the device. Was it activated by cooking, dust, steam, an aerosol, a contractor? Make the entry specific.
4. Reset only after the cause is identified or after consultation. Multiple resets without diagnosis is how a chronic false alarm pattern gets established.
5. Notify the ARC if monitored.

When to escalate

Three false alarms from the same device in twelve months is a pattern. Five is a problem. Either way, that device needs investigation — not another reset.

Email hello@eburyfire.co.uk with the Log Book entries and we'll diagnose remotely before booking a site visit if we can.