Where should smoke alarms go and how many do I need?

Most homes have too few alarms, in the wrong places, and nobody has tested them this year. Getting the positions right is a single afternoon and it is the highest-value safety work in a house.

Safety

Step by step

1. Start with one on every floor.In the hallway or landing — the escape route. That is the legal minimum in most of the UK and the absolute floor rather than a target.
2. Add alarms in the rooms that matter.Any room with a fire, a heater, or where electrical items are left charging — living room, bedrooms, home office. Scotland requires an alarm in every room used as a living room or bedroom.
3. Use a heat alarm in the kitchen.A smoke alarm in a kitchen triggers on toast and gets disabled within a week. A heat alarm responds to a rapid temperature rise instead, which is what you want there.
4. Mount on the ceiling, in the middle of the room.Smoke rises and spreads across a ceiling. Central is best; if you must use a wall, it goes 15-30cm below the ceiling, and never in the corner where the two meet — air is still there.
5. Keep clear of walls, lights and vents.At least 30cm from any wall or light fitting, and away from air vents, extractor fans and windows, all of which move smoke away from the sensor.
6. Do not put one in a bathroom.Steam sets off smoke alarms reliably. If you need cover nearby, put it outside the door in the hallway.
7. Add a carbon monoxide alarm where there is a fuel-burning appliance.Boiler, gas fire, wood burner, or a flue passing through. A carbon monoxide alarm is a different device from a smoke alarm and is positioned differently — roughly at head height, one to three metres from the appliance.
8. Interlink them if you can.Interlinked alarms all sound when one detects, which matters enormously at night and across floors. Radio-interlinked battery models avoid any wiring.
9. Choose sealed ten-year batteries.A sealed lithium unit removes the annual battery change and the temptation to borrow the battery for something else. Replaceable-battery alarms are the ones that end up silent.
10. Test monthly and replace after ten years.Press the test button on each alarm once a month. Sensors degrade — every alarm has a manufacture or expiry date printed on it, and after about ten years it needs replacing whatever the battery says.

Tips

• Write the replacement date on the alarm in marker when you fit it. Nobody remembers otherwise.
• If an alarm chirps intermittently, that is the low-battery or end-of-life warning. Note which it is before assuming a battery will fix it.
• Alarms for deaf and hard-of-hearing people, with vibrating pads and strobes, are available and often free from local fire services.

Common mistakes

• Putting a smoke alarm in the kitchen — Cooking sets it off constantly, so it gets muted or removed. A heat alarm covers a kitchen without the false alarms.
• Taking the battery out to stop nuisance alarms — It is the commonest cause of a fatal fire in a house that had an alarm. Move the alarm or fit the right type instead.

If it doesn't work

Questions people ask