What is this?
A smoke detector that does not work when tested is a serious safety issue. Whether battery-powered or mains-wired, a non-functioning smoke alarm means you would not get early warning of a fire. UK fire services recommend testing all smoke alarms weekly by pressing the test button.
Common causes
- Dead or missing battery
- Detector has reached its 10-year end of life
- Sensor heavily contaminated with dust, grease, or paint
- Mains supply interrupted (for mains-wired detectors)
- Detector has been painted over during decorating
- Faulty detector — manufacturing defect or damage
Is it dangerous?
A non-working smoke detector is a high safety risk. Smoke alarms provide the early warning that saves lives — most fire deaths in the UK occur in homes without working smoke alarms. Replace or repair a faulty smoke alarm immediately. Fit a temporary battery alarm if you cannot fix the mains one right away.
Can I fix it myself?
Replace the battery first — this solves most non-working smoke alarms. For mains-wired units, check the consumer unit for a tripped MCB. Test the alarm by pressing and holding the test button. If the alarm is over 10 years old, replace it — check the manufacture date on the back. If the alarm has been painted over, replace it as paint blocks the sensor.
When to call an electrician
Call an electrician if your mains-wired smoke alarms need replacing, if the alarm circuit has a fault, if you need to upgrade from battery to mains-wired alarms, or if you are a landlord needing to comply with smoke alarm regulations.
What will an electrician do?
Test existing smoke detectors and the alarm circuit
Replace end-of-life detector heads
Repair any wiring faults on the alarm circuit
Install new mains-wired smoke alarms where required
Ensure compliance with Building Regulations and rental property requirements
Typical cost
£60 – £250
Replacing detector heads on an existing mains circuit is straightforward. Installing a new mains-wired system involves more work and costs more.
