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Fire safety 101: How many smoke alarms do I need?

Fire safety 101: How many smoke alarms do I need?

Concerning statistics from a Government report in 2022 revealed a smoke alarm was not present in 24% of all dwelling fires, and a further 37% of all dwelling fire-related fatalities. We’ve created a comprehensive guide to answer the common question: ‘How many smoke alarms do I need?’ and everything else you need to know to protect your loved ones, property and belongings.

How many smoke alarms do I need in each room?

Advice from the UK Government recommends having a smoke alarm on the ceiling of every level in your home or accommodation. Smoke detectors have a limited range, so if you have a large property or an unusual floor plan, it would be safer to increase this as required.

Other sources such as the National Fire Protection Agency suggest having additional alarms in bedrooms and rooms with multiple appliances plugged into the mains.

Smoke and steam may activate your alarm unnecessarily, and the London Fire Brigade suggests to place these away from bathrooms and kitchens in a corridor or hallway. Heat alarms are better suited to kitchens and bathrooms.

Alongside your smoke alarm, it is wise to have a carbon monoxide detector, to alert you to any abnormal levels of the poisonous gas. This goes the same for heat alarms, which will detect high temperatures inside your property.

The different types of smoke alarms

There are two different types of smoke alarms and a combination of these currently on the market.

Ionization smoke alarm

An ionization smoke alarm uses a radioactive substance, electrodes (conductive plates or wires), and a power source (such as a battery) to create a current flow. The radioactive substance decays and emits particles which ionize the air, attracting charged gas molecules to the electrodes which create the current.

When smoke particles enter the chamber, the ionization process is disrupted, stopping the current. An electric circuit monitors this, and triggers the alarm if it stops.

The ionization alarm is considered an older technology and can be more prone to more nuisance false alarms from cooking etc. It is generally advised these alarms are better situated away cooking appliances.

Photoelectric / optical smoke alarm

A photoelectric or optical smoke alarm uses the light scatter principle, and identifies smoke particles by pulsing a straight beam of infrared light into a chamber every few seconds. If smoke particles enter the chamber and reflect the light ray on to the sensor, the intensity or abnormal pattern of light distribution is detected which activates the alarm.

Dual detector smoke alarm

Dual detectors are aptly named as they contain both ionization and photoelectric/optical smoke detection technology.

This may seem ideal, however some dual detectors are unreliable as they require both the ionization and optical sensors to be triggered before sounding the alarm. This means you are relying on the slowest detectors reaction time.

If it is not clear from the product box or manufacturer’s instructions on how the smoke detector operates, the National Fire Protection Association advises it would be safer to opt for purchasing both an ionization and a photoelectric smoke detector.

Ionization vs. Photoelectric/ Optical smoke alarm

Experimental research on each alarm suggests their performance depends on the stage and type of fire, for more in-depth information on the types and stages of fire, read our blog; How does fire spread?

Ionization alarms are particularly sensitive to the fast flaming stage of a fire, which produces fine smoke particles. Photoelectric/ optical alarms are better at detecting visible smoke from slow burning, smouldering stages of fire.

Fast flaming fires erupt quickly and do not provide the same smoulder of smoke, and ionization alarms may not perform as well in smoky conditions. Manufacturers and governing bodies are beginning to phase out ionization alarms – the National Fire Chiefs Report delves further into the reasonings behind this.

Whilst both effective, if you have a choice between the two, the photoelectric/optical alarm is considered the better option by some manufacturers and governing bodies. However, opting for both alarms will ensure you are covered in every eventuality.

Battery vs. mains powered smoke alarms

Statistics from the International Fire and Safety Journal show in England during 2020/21, 28% of smoke alarms failed, increasing to 39% in Scotland and 50% of all fires in wales. Ensuring the efficacy of your alarm could be paramount to protecting yourself and your property.

Whilst there is no official advice provided by the government, there are obvious conclusions we can make when considering battery vs mains powered smoke alarms.

Battery powered alarms rely solely on the battery, which can and do go flat. Although a completely viable option, it is imperative to regularly test and change these.

Woman changing smoke alarm batteries.

On the other hand, alarms powered through the mains are more reliable as they have a consistent power supply. For power outages, they have a backup battery which activates when the mains fail.

Testing is still essential for mains powered alarms, but you are more protected from power supply failure.

If opting for a battery powered smoke alarm, the government advises choosing ‘sealed for life’ over standard batteries, which are lithium and are manufactured to have a 10 year life span. This eliminates the need to replace batteries over this period, although you will have to repurchase the whole device once this has elapsed.

Budget vs. high quality smoke alarms

Whilst it may be tempting to save some pennies and go for the cheaper option, there are some things you should consider before making this decision.

Name brand smoke alarms with a higher price tag, tend to be more quality-assured as they are rigorously tested. They are also more likely to be compliant with British legislative standards BS 5839-6.

It is also important to be aware of budget manufactured alarms which may seem like a steal, but are less effective, faulty or non-compliant. Higher quality alarms will also reduce the frequency of nuisance false alarms.

It is important to pick a smoke alarm that is convenient for your needs, and provides you with adequate safety protection. Do thorough research on your options and ensure they are complaint to British Standards.

If you do not have the resources to be able to purchase your own smoke alarms, you may be eligible for support. Local fire brigades across the UK provide ‘Home Fire Safety Visits‘, where they can install smoke alarms for free.

You can use the Government’s site Fire England to search for your local fire authority and check your eligibility.

How often should they be tested?

The UK Government advises you should test your smoke alarms at the very least monthly, or weekly if you have a commercial property. Batteries should be replaced yearly, and you should never remove the batteries if a false alarm sounds.

Some alarms may require maintenance and cleaning, by removing dust or built up grime.

Man testing smoke alarm.

A warning about fire insurance policies

If you hold a fire insurance policy, ensure you read the terms and conditions of your coverage thoroughly. Some policies have a clause which voids claims where damage could have been avoided due to a lack of smoke alarm, or one with flat batteries.

For more essential guidance and advice on fire safety, please take a look at our blog Surviving a House Fire: Emergency Guide.

If you are unfortunate enough to have suffered from the devastation of a fire, we can help. We have over 50 branches across the UK, meaning no-matter where you are situated we can reach you.

We provide unparalleled smoke and fire restoration services, which will restore your property and help your house feel like a home again. You can contact us on our 24-hour helpline 365 days a year on 01624 422 488.

Published: 16 Jun 2023