What is this?
A burglar alarm that triggers false alarms is a common and frustrating problem. In the UK, persistent false alarms can lead to police response being withdrawn under ACPO guidelines after a certain number of confirmed false activations. Neighbours may also complain, and some local authorities can issue noise abatement notices.
Common causes
- Faulty or oversensitive PIR (passive infrared) sensor
- Spider or insect inside a sensor triggering the detector
- Sensor detecting pets (if not a pet-friendly sensor)
- Loose sensor or door contact
- Low battery in a wireless sensor
- Environmental factors — draughts, moving curtains, or heating activating near a sensor
Is it dangerous?
False alarms are not an electrical safety risk but they are a significant nuisance. Frequent false alarms also lead to alarm fatigue where you or neighbours start ignoring the alarm, which defeats its purpose.
Can I fix it myself?
The alarm panel should show which zone triggered the alarm. Check that sensor for obvious issues — is it loose? Is there a spider web inside? Is a curtain or blind moving in front of it? Try masking one zone at a time to isolate which sensor is causing the problem. Clean sensors gently with a dry cloth.
When to call an electrician
Call an electrician or alarm specialist if you cannot identify which sensor is causing false alarms, if cleaning and checking sensors does not help, if you need pet-immune sensors fitted, or if the system has been false alarming for a while and you have not been able to resolve it.
What will an electrician do?
Review the alarm log to identify the triggering zone and pattern
Inspect and test each sensor on the problem zone
Clean or replace faulty sensors
Adjust sensor sensitivity or angle
Fit pet-immune sensors where needed
Test the complete system after repairs
Typical cost
£60 – £200
Sensor replacement or adjustment is the most common fix. Replacing multiple sensors or upgrading to pet-immune units will cost more.
