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How we test smoke alarms

By Joanna Pearl

To uncover the Best Buy smoke alarms that you can trust, we put every smoke alarm we review to the test against four different types of fire.

Put us to the test

Our Test Labs compare features and prices on a range of products. Try Which? to unlock our reviews. You'll instantly be able to compare our test scores, so you can make sure you don't get stuck with a Don't Buy.

Our video above shows how a Best Buy smoke alarm will make a real, practical difference to you. Read on for more on our tests and how we uncover the smoke alarms you can trust.

We put the alarms through independent and rigorous tests in accordance with the British Standard. Our four fires in a specially designed test room represent the extremes you could face – from a cigarette smouldering on a sofa to a chip-pan fire.

Our reviews answer the most crucial questions about smoke alarms.

  • Will this smoke alarm go off in every fire?
  • Is it loud enough to wake my family?
  • Is the light bright enough to be seen in smoke?
  • Will it cause nuisance alarms?
  • Is it simple to install and maintain?
  • Should I buy it?

Find out which models give top-class results in our smoke alarm reviews.

Will this smoke alarm go off in every fire?

Our smoke alarm tests are designed to put smoke alarms through all the extremes they could be exposed to in a normal house fire. The fires include a smouldering wood fire, a smouldering cotton fire, a flaming liquid fire, and a flaming plastics fire. 

A house fire is usually made up of more than one type of fire, so it's important that an alarm can respond to every type.

Is it loud enough to wake my family?

The smoke alarms are also tested in a soundproofed (fully anechoic) chamber, to ensure they’re loud enough to wake your family in time to escape a fire. 

This sound chamber absorbs all sound from the outside world so we can accurately measure the exact decibel output when the smoke detector sounds.

Only the fastest and clearest models earn our recommendation as Best Buy smoke alarms. We highlight the worst as Don't Buy smoke alarms that we think you should avoid.

Is the light bright enough to be seen in smoke?

Where the smoke detectors on test had escape lights, we tested their visibility in smoke from 10 metres away. You wouldn't expect the lights on your smoke alarm to illuminate the room, but they should help orientate you in smoky conditions.

Will it cause nuisance alarms?

And we’ve included ‘nuisance alarm’ tests – such as burning toast and steam from a shower – to see how the alarms respond, as these are the situations that encourage people to disable their alarms.

Is it simple to install and maintain?

We test how easy it is perform the basics to get your smoke alarm up and running - such as installing it, and changing the battery. These essential tasks form our ease of use score.

Should I buy it?

80%the score a smoke alarm needs to earn our Best Buy logo

All the assessments listed above go into making the final overall score for each smoke alarm we review. And because some factors are more important than others, they carry different weights in our calculations.

The overall test score we award to each smoke alarm scores ignores the price of the monitor and is instead based on the following factors:

  • 80% Performance (including fire and sound output tests)
  • 20% Ease of use (including ease of installation and battery changing)

A model has to achieve 80% or more to earn our Best Buy recommendation and anything scoring 20% or less is a Don't Buy which we think you should avoid.

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