Smoke Alarms: Which to Buy and Where to Fit Them (UK Guide)

A working smoke alarm roughly doubles your chance of surviving a house fire, and the danger rises in autumn and winter: heaters, candles, log burners, overloaded sockets and electric blankets all come out, and more fires start after dark when people are asleep. A fire fills a house with smoke and toxic gas long before flames reach the bedrooms, so the alarm buys you the minutes you need to get out. This guide covers which type to buy, how many, and — just as importantly — where UK guidance and the law say to fit them.

First, the one thing every smoke alarm must have

Only buy an alarm marked to BS EN 14604 — that's the British and European standard for domestic smoke alarms. Look for a Kitemark or other genuine third-party certification rather than a self-declared CE mark alone. This matters more than brand or price: an uncertified detector bought cheaply online may respond too slowly, or not at all, to a real smouldering fire. If a listing doesn't clearly state EN 14604, skip it.

Optical, ionisation or heat — which type?

Optical (photoelectric) alarms

These are the sensible default for most rooms. They use a light sensor and respond fastest to the larger, smouldering smoke particles from things like overheating wiring, upholstery and bedding — the slow, deadly fires that start while you sleep. They're also less prone to nuisance triggers from cooking than the old ionisation type. If you buy one kind of alarm for landings and bedrooms, make it optical.

Ionisation alarms

These detect the tiny particles from fast, flaming fires slightly quicker, but they're far more likely to false-alarm near kitchens and bathrooms, which is exactly why people take the battery out — the worst outcome. They've largely fallen out of favour for domestic use; most UK fire services now recommend optical alarms for general protection. There's no need to seek an ionisation unit out.

Heat alarms

A heat alarm triggers on temperature, not smoke, so it won't nuisance-trip on toast or steam. That makes it the right choice for the kitchen and sometimes the garage — a smoke alarm there would be silenced within a week. Fit a heat alarm in the kitchen and optical smoke alarms everywhere else, and ideally interlink them (below) so the kitchen unit still wakes the whole house.

Sealed 10-year or replaceable batteries?

Sealed 10-year alarms

These have a lithium battery built in for the certified life of the alarm — usually ten years — then you replace the whole unit. They're the best default for most households: nothing to forget, no flat battery on the night it matters, and low cost per year. Note the expiry date printed on the back, because the sensor itself ages: a smoke alarm is not forever, and one over ten years old should be replaced even if it still beeps.

Replaceable-battery alarms

These take standard cells you swap yourself. They're cheaper up front but only as reliable as your memory to test them and change the battery. The classic failure is a chirping alarm silenced by pulling the battery and never replaced. If you'll genuinely test monthly and change cells promptly, they're fine; if not, a sealed 10-year unit removes the human error.

Interlinked alarms — worth it, and increasingly required

In a standalone alarm, only the unit that senses smoke sounds — which is useless if the fire starts downstairs while you sleep upstairs. Interlinked alarms all sound together the moment any one detects smoke, so you're woken by the alarm nearest your bed even if the fire is at the far end of the house. Wireless (radio-frequency) interlinked kits let you retrofit this without running cables: you pair the units once, and they talk to each other. For any home over one storey, interlinking is the single biggest upgrade you can make.

This is now the legal standard in parts of the UK. Since February 2022 every home in Scotland must have interlinked alarms — optical or heat alarms in the right rooms, all linked. In England, the Smoke and Carbon Monoxide Alarm Regulations require landlords to fit a smoke alarm on every storey of rented homes, and building regulations (Approved Document B) call for mains-powered, interlinked alarms in new and materially altered homes. Even where you're not legally obliged, interlinked alarms are the standard to aim for.

How many, and where to fit them

As a minimum, fit at least one smoke alarm on every storey of the home, on the ceiling of the hallway and landing — the escape routes. Add an optical alarm inside any room where a fire is more likely or where someone sleeps with the door shut, such as a living room with a log burner or a bedroom used by a smoker or someone with limited mobility. Fit a heat alarm in the kitchen and the garage. Unlike a CO alarm, smoke rises, so a smoke alarm belongs on the ceiling, at least 30cm from any wall or light fitting; if it must go on a wall, keep it 15 to 30cm below the ceiling. Keep alarms away from bathrooms and directly above cookers, where steam and fumes cause false alarms.

What the beeps mean and looking after them

Learn the sounds before there's an emergency. A continuous loud sounding is the real thing — get everyone out, stay out, and call 999; don't stop to gather belongings or investigate. A single chirp every 30 to 60 seconds is a maintenance prompt, usually a low battery or that the alarm has reached end of life — sort it, don't silence and forget it. Test every alarm monthly with the button, gently vacuum the dust off the vents a couple of times a year, and note each unit's expiry date in your phone. Also plan the practical side: agree an escape route and a meeting point with the household, and keep a torch or a head torch by the bed so you're not fumbling for light in smoke.

A sensible plan for most UK homes

For the average home the best-value setup is EN 14604 sealed 10-year optical alarms on every landing and hallway ceiling plus the living room, a heat alarm in the kitchen, and — ideally — a wireless interlinked set so they all sound together. Pair this with a carbon monoxide alarm in any room with a fuel-burning appliance, because smoke alarms do not detect CO. Test monthly, replace any unit over ten years old, and treat working, interlinked smoke alarms as the baseline of home safety rather than an optional extra. It is one of the cheapest life-saving purchases you can make.