Smoke alarm going off when you cook? How to stop false fire alarms
A smoke alarm that goes off over the toaster, the kettle or a hot shower is usually the wrong type of alarm in the wrong place. Steam, cooking fumes, aerosols and dust put particles in the air that a smoke sensor can mistake for smoke. Move smoke alarms back from kitchen and bathroom doors, fit a heat alarm in the kitchen and replace alarms over ten years old. Never take the battery out.
Why does a smoke alarm go off for no reason?
A smoke alarm reacts to particles in the air, and plenty are not smoke. Ajax and UK fire services name these triggers:
| Trigger | Where it happens | What helps |
|---|---|---|
| Steam | Bathroom and kitchen doorways | Move the smoke alarm further away |
| Cooking fumes | Kitchens, open-plan living areas | A heat alarm in the kitchen |
| Aerosols and vaping | Bedrooms and landings | Spray and vape well away from it |
| Dust and insects | Building work, dusty rooms | Protect alarms during work, then check them |
| Draughts and heat | Fans, vents, windows, heaters | Re-site the alarm |
| Age | Alarms past their replace-by date | Replace the whole unit |
Northamptonshire Fire and Rescue Service says contamination by dust and small insects is the most common cause. Ajax adds testing a monitored system without warning the monitoring centre first.
How common are false fire alarms?
Very. Government (MHCLG) figures for England show fire and rescue services attended 255,047 fire false alarms in the year to March 2026, 40% of all incidents. Of those, 172,247 were due to apparatus, meaning alarm or fire-fighting equipment started the call.
London Fire Brigade says it attended around 52,000 false alarms from automatic fire alarms between April 2023 and March 2024, and that fewer than 1% of automatic alarms are real fires. Since October 2024 it no longer attends automatic alarms at most non-residential buildings between 7am and 8.30pm unless a fire is reported. Homes still get a response.
What should you do when it goes off over cooking?
- Check first. If you cannot see the cause, get everyone out and call 999.
- Clear the air. Open a window and let the alarm reset.
- Use the button, not the battery. Northamptonshire Fire and Rescue Service says never to disconnect an alarm or remove its batteries after a false alarm.
- Fix the cause. If it keeps happening, move the alarm or swap it for a heat alarm.
On an Ajax system, the app names the detector and room that raised the alarm. Press the centre of a FireProtect 2 to mute it, or mute from the app, a keypad or a Button set up for it. Muting lasts up to 10 minutes, the alarm returns if another detector senses smoke or heat, and Ajax says a detector will not mute at critical smoke levels.
Where should alarms go to avoid false alarms?
- Kitchen: heat, not smoke. London Fire Brigade advises a heat alarm there, because cooking fumes do not set it off.
- Smoke alarms back from steam. London Fire Brigade and Northamptonshire Fire and Rescue Service say to keep them away from kitchens and bathrooms.
- Away from moving air. Ajax's FireProtect 2 manual rules out spots near fans, vents, open windows and doors, heaters and room corners.
- Garages. Because of exhaust fumes, the same manual points to the Heat/CO model there.
- On the ceiling, or high on a wall only where the instructions allow (London Fire Brigade).
Exact spacings for new homes and alterations come from BS 5839-6, the code of practice installers work to.
What do the rules say about kitchens?
| Where | What the rules ask for |
|---|---|
| Scotland, all homes | Smoke alarms in the most-used room and every hall and landing, a heat alarm in the kitchen, all ceiling-mounted and interlinked. A CO detector in any room with a boiler, open fire or wood burner. |
| England, new homes | Approved Document B: mains-powered smoke alarms (BS EN 14604) and heat alarms (BS 5446-2) with standby power, to at least Grade D2 Category LD3 of BS 5839-6. |
| England, rented homes | A smoke alarm on every storey with living space and a CO alarm in rooms with a fixed combustion appliance other than a gas cooker. Since 1 October 2022, landlords must repair or replace an alarm once told it is faulty. |
| Wales, rented homes | Mains-powered, linked smoke alarms on every storey, and a CO alarm in rooms with a gas, oil or solid-fuel appliance. |
A tenant who pulls down a nuisance alarm leaves the landlord a fault to fix, so fit the right type first and check with your installer or council which alarms comply.
How does Ajax FireProtect 2 tell smoke from steam?
- Two colours of light. A dual-spectrum optical sensor with blue and infrared LEDs judges particle size as well as density. Ajax says its HazeFlow 2 algorithm uses this to separate smoke from steam, and its specifications say the smoke models ignore water vapour.
- A protected chamber. Ajax's patented chamber is designed to keep out dust, dirt and insects.
- Heat sensing. The heat sensors alarm above 64°C, or on a rise of more than 10°C in a minute or less.
- Self-checks. Detectors check their batteries and sensors and report faults through the hub.
- Ten-year life. Ajax recommends replacing a detector after ten years, when sensitivity falls.
| Ajax model | Senses | Power | Our price inc VAT |
|---|---|---|---|
| FireProtect 2 SB (Heat) kitchen heat alarm | Heat | Sealed battery | £111.93 |
| FireProtect 2 SB (Heat/CO) | Heat, CO | Sealed battery | £150.00 |
| mains FireProtect 2 AC (Heat/Smoke) | Heat, smoke | Mains, backup battery | £80.77 |
| FireProtect 2 RB (Heat/Smoke) | Heat, smoke | Replaceable batteries | £98.07 |
| sealed-battery SB (Heat/Smoke) | Heat, smoke | Sealed battery | £122.30 |
Prices include VAT, delivery is extra, and prices can change. The Heat/CO model suits a kitchen with a boiler. Each alarm sounds on its own through an 85 dB siren (at 3 m). Add a Hub 2 (2G) alarm panel (£161.53) and they interconnect, so a fire in one room sets off the others and alerts reach the app. See the Ajax wireless fire alarm range.
Can you see what set it off before you go and look?
Yes, with a camera on the hub. The MotionCam U (PhOD) photo detector (£136.15) can take photos when another Ajax detector goes off, a setting Ajax ships switched off. At the default resolution a photo reaches the app in up to 9 seconds. Cameras such as the Ajax IndoorCam (£191.69) can record a clip when a detector triggers; browse Ajax cameras and NVRs, or pick the Hub 2 (4G) (£228.45) for 4G rather than 2G. In a let property, agree any indoor camera with the tenants first.
Our take
Most nuisance fire alarms are cured by changing the alarm or its position, not by adding more. Put a heat alarm in the kitchen, keep smoke alarms back from steam and replace old units. Zenith Security Co. has supplied security equipment since 2012. We supply Ajax fire alarms rather than fit them; London Fire Brigade says mains alarms should be fitted by a qualified electrician, and we can recommend a qualified installer depending on the job and area. For commercial systems, see our fire alarm equipment, or everything we stock from Ajax.
Want help choosing? Call 01902 902251, contact us online or visit our Wolverhampton trade counter. We ship nationally to England, Scotland and Wales.
Smoke alarm false alarms: quick questions
Why does my smoke alarm go off when I shower?
Steam is reaching it from the bathroom. Move it further away.
Can I put a smoke alarm in the kitchen?
Fire services advise a heat alarm instead. In Scotland, a kitchen heat alarm is the law.
Is it safe to take the battery out?
No. Silence it with the button and only remove a battery to replace it.
Why does my smoke alarm chirp at night?
Usually a low battery, says Northamptonshire Fire and Rescue Service. Ajax detectors give 30 days' warning, in the app via a hub.
Do Ajax fire alarms need a hub?
No. A hub links them, sends phone alerts and allows photo checks, though mains AC models can also link without one.
Source: Ajax Systems blog, 31 Aug 2026, with MHCLG fire statistics, London Fire Brigade, Northamptonshire FRS, gov.scot, Approved Document B and legislation.gov.uk (England, Wales). Device figures are Ajax's own.
