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A guide to smoke alarms

Making sure you have the right smoke alarm and that it’s working properly can keep your home safe and minimise costly fire damage.

GoCompare author
Updated 29 November 2021  | 4 mins read

What’s a smoke alarm?

A smoke alarm is a single unit or an interlinked alarm system that detects and warns you about the presence of smoke in your house.

Key points

  • You should have at least one smoke alarm on every floor of your home
  • Smoke alarms aren’t suitable for kitchens, but heat alarms are
  • A combined alarm that contains smoke and heat sensors can give you the best detection and help avoid false alarms
  • Some alarms can be interlinked so when one alarm is triggered the other units are also set off
  • Make sure your alarm has a British Standards or European (CE) safety mark

Do I need a smoke alarm to buy home insurance?

Nearly all home insurance policies cover you for fire damage to your property and belongings as standard.

And while you don’t need a smoke alarm to buy home insurance, putting safety measures like this in place can help to reduce your premiums.

However, it’s a condition of many insurers that if you’ve told them your home has smoke detectors, they must work.

If it’s discovered your smoke alarms weren’t working properly or that batteries hadn’t been replaced at the time of a fire, insurers may reduce your payout or reject your claim in full.

Types of smoke alarm

There are lots of different types of smoke alarm you can choose from. Which one will suit you best will typically depend on where you need to install it in your home:

Ionisation

Ionisation smoke detectors work by creating a small electric current inside them and tend to be the cheapest type of alarm you can buy.

If smoke particles enter the alarm unit, it changes the current. This internal change sets off the alarm to let people know about the fire before the smoke gets too thick.

These alarms are more sensitive to smoke from fast-burning fires. Their sensitivity means they’re prone to being set off by cooking fumes, so they’re not suitable in or near kitchens.

Optical alarms

These alarms are light sensors and use infra-red beams to check for smoke.

Optical alarms are more expensive but more effective than ionisation units at detecting large particles of smoke from slow, smouldering fires - like those caused by wiring faults.

This type of alarm can be installed near kitchens because it’s less likely to be triggered by things like burning toast.

Heat alarms

Also called a thermal alarm, this type of smoke alarm detects an unexpected rise in temperature.

Detecting heat rather than smoke, once the air temperature reaches around 58°C the alarm will be set off. This makes them slower to respond than smoke alarms.

Because heat alarms aren’t sensitive to smoke, they’re ideal for kitchens and garages. But as they only cover quite a small area, you may need more than one for larger spaces.

Multi-sensor

A combined or multi-sensor alarm can detect smoke and heat. This makes it much quicker at detecting a fire and means false alarms are much less likely.

Multi-sensor alarms are speedy at responding to different types of fire, whether it’s one that’s fast-flaming or smouldering.

This type of alarm can be used for bedrooms, living rooms, dinings rooms, and landings and hallways.

Smart smoke alarms

As with other smart solutions, smart smoke alarms send an alert to your smartphone or mobile device when smoke is detected, as well as sounding an alarm.

Some smart smoke alarms can also be connected to other smart home solutions. For example, turning your smart lights on to help you see through the smoke.

Most smart smoke alarms use optical sensors to detect smoke particles and some can also provide carbon monoxide detection. They also test themselves on a regular basis, rather than you having to do it manually.

What type of smoke alarm do I need?

When you’re buying a smoke alarm it’s important to buy it from a reputable company and for it to meet British safety standards. Our tips for choosing the right alarm are:

  1. Check it’s been certified to the British or European Standard

    The British Standard code of practice for fire detection in homes is BS5839. To make sure your alarm is designed to these standards, check it has the well-known Kitemark or CE safety mark.

  2. Decide what power source you’ll need

    You can either buy battery-powered smoke alarms, or you can opt for more costly mains-powered alarms. These need professional installation but provide peace of mind with their continuous power supply.

  3. Use the right alarm for the right area

    The general rule from the UK Fire Service is to use heat alarms for the kitchen and garage. For bedrooms, living rooms and hallways use optical or combined alarms. And for hallways use ionised or combined alarms.

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What are the different grades and categories for home smoke alarms?

The British Standard BS5839, has different grades and categories of smoke detection systems for homes:

Alarm grades D1 and D2

These are for mains-powered, interlinked smoke detectors, and heat alarms. They are usually powered with a cable from the nearest light fitting. Alarms on interlinked systems need to be connected with cables between each unit or by a radio interlink connection.

Alarm grades F1 and F2

These are battery-powered smoke detectors and heat alarms. You can install these without needing to use an electrician and most are individual units, but some use wireless technology so that they can be interlinked.

How many smoke alarms should I have in my home?

You should have at least one smoke alarm on every level of your home - they should be put in hallways and landings.

And while you don’t legally have to have a smoke alarm in every room, the more alarms you fit, the more protection your home will have.

Where should I fit my smoke alarms?

Because smoke rises, the ideal position is in the middle of the ceiling of the room, hallway or landing.

Smoke alarms should be put at least 30cm away from any wall or light fitting.

Also keep them well away from fans, vents, and other well-ventilated areas that can blow smoke away from smoke detectors.

To make sure you’re alerted to a fire as quickly as possible, install smoke alarms near to where you sleep - but don’t put them in the bathroom as steam may trigger the alarm.

Smoke alarm maintenance

Only working detectors save lives so It’s important to look after your smoke alarm.

According to UK government statistics, between April 2020 and March 2021, the smoke alarm battery was missing or defective in 18% of homes where there had been a fire.

To keep your smoke alarm in good working order you should:

  • Test your alarm once a month by pressing the test button
  • Vacuum it regularly using the brush attachment to keep the sensors dust-free
  • Change the battery - change alkaline batteries once a year and lithium batteries after five years
  • After ten years replace the whole system

For a free reminder to check your smoke alarm, you can sign up to the Safelincs Smoke Alarm Reminders Service.

Where can I buy a smoke alarm?

Smoke alarms are easy to get hold of and you can buy them from a variety of places including DIY stores, supermarkets and online.

If you’re buying one that’s going to be connected to your mains supply, you’ll need to use an electrician to fit it.

Make sure you buy one from a reputable company and that any alarm has the British Standards or European safety mark.

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