If your smoke alarm is sounding continuously, first check there is no smoke or fire in your property. If no fire or smoke is present, or the alarm is beeping intermittently, there are three main reasons why this may be happening:
Read our in-depth smoke alarm troubleshooting guide to find a full list of reasons and solutions.
Optical smoke alarms, also known as photoelectric detectors, have a high sensitivity to large particles in the air. They are slightly quicker at detecting slow-smouldering fires that produce a lot of smoke (such as fire from soft furnishings). They are suitable for living rooms and sleeping areas and are used near kitchens as they are less prone to false alarms.
Ionisation smoke alarms use a small amount of radioactive material in the sensor chamber to detect fires, as such they are being discontinued. Safelincs encourages customers to purchase optical smoke alarms instead.
See also heat alarms for the most suitable protection in a kitchen.
Read more about how different smoke alarms work.
The best location to install your smoke alarm is in the centre of the ceiling rather than on the wall.
During a fire, smoke initially rises and then spreads horizontally. Placing the smoke alarm in the centre of your ceiling means that it is closest to all four points of your room. This ensures that you receive the earliest possible warning of a fire.
For more information, read our guide to positioning your smoke alarm and guide to which smoke alarms are best for each room.
Smoke alarms can be either screwed to the ceiling using the holes on the base plate (screws provided), or fixed in place using either a self-adhesive sticky pad or a self-adhesive magnetic mounting kit.
The only way to detect the presence of carbon monoxide, also known as the silent killer, is by installing a carbon monoxide alarm, as it cannot be detected by human senses. A carbon monoxide detector will sound an alarm if the CO concentration is higher than permitted.
Each year, over 50 people die in the UK from exposure to carbon monoxide. Many more people die through strokes and respiratory illnesses made worse by inhaling low levels of CO over prolonged periods.
To protect you and your family, purchase a carbon monoxide detector and use the test button weekly to check it is in working order.
You can reduce the risk of CO poisoning by:
There is no legal or BSI requirement to test CO detectors with a test gas. It is usually sufficient to check your CO detector is working by using the test button on the detector. For peace of mind sign up to our free reminder service.
We recommend using an optical smoke alarm in hallways, living rooms, dining rooms and bedrooms, as they are good at detecting smouldering fires from soft furnishings and are less likely to be set off by cooking fumes from a connected kitchen.
Heat alarms are recommended for kitchens and garages as they do not sound false alarms from cooking fumes, vehicle fumes or steam.
Ionisation alarms are being phased out due to the small amount of radioactive material used in the detector chamber. Safelincs recommends optical smoke alarms where ionisation alarms were previously used.
| Concentration of CO in the air | Implications of Exposure |
| 10 parts per million (ppm) | Threshold at which prolonged exposure can have adverse effects on the body and brain. This can include neuropsychological and cardiovascular issues. |
| 50 parts per million (ppm) | Safety level as specified by the Health and Safety Executive for a maximum of 30 minutes. |
| 200 PPM | Slight headache within 2-3 hours. |
| 400 PPM | Frontal headache within 1-2 hours, becoming widespread in 3 hours. |
| 800 PPM | Dizziness, nausea, convulsions within 45 minutes, insensible in 2 hours. |
CO detectors should be installed near potential sources of carbon monoxide, essentially any fuel-burning appliances. As you are likely to be most affected by CO in areas of your home that you spend the most time in it is advisable to install alarms in those areas as well, such as at head height in the living room and bedrooms. If your property has an attached garage with a connecting door through to the house, it is recommended to fit a CO alarm inside the house leading from that doorway.
Carbon monoxide has been proven to spread into neighbouring properties through open windows, as well as through loft spaces in semi-detached or terrace houses.
Battery powered carbon monoxide alarms can typically be installed wall-mounted or left free-standing on flat, level surface. Combined smoke & CO alarms or mains-powered CO alarms are typically installed on the ceiling.
Do not install CO alarms within 3 metres of doors or windows, above radiators, or immediately close to anything that gives off steam or fumes like a cooker or shower room. Similarly, it is not recommended to install detectors in dusty areas such as workshops or garages.
For more information, please check the manufacturer's instructions – you can download the PDF manual from the relevant product page on our site. You can also watch our video guide to positioning CO detectors.
CO detectors should be installed near potential sources of carbon monoxide, essentially any fuel-burning appliances such as boilers, cookers and ovens, fireplaces (both open and enclosed burners), and portable generators. As you are likely to be most affected by CO in areas of your home that you spend the most time in it is advisable to install alarms in those areas as well, such as the living room and bedrooms. It is also worth noting that while one detector is better than no detectors at all, larger homes may require several detectors to cover the property fully.
Also note that carbon monoxide has been proven to spread into neighbouring properties through open windows and, in semi-detached or terrace houses, through loft spaces. If your property has an attached garage with a connecting door through to the house, it is recommended to fit a CO alarm inside the house leading from that doorway.
Battery powered carbon monoxide alarms can typically be installed wall-mounted or left free-standing on flat, level surface.
Combined smoke & CO alarms or mains-powered CO alarms are typically installed on the ceiling and should be at least 30cm away from any wall, light fitting, or other obstruction.
Do not install CO alarms within 3 metres of doors or windows, above radiators, or immediately close to anything that gives off steam or fumes like a cooker or shower room. Similarly, it is not recommended to install detectors in dusty areas such as workshops or garages.
For more information, please check the manufacturer's instructions – you can download the PDF manual from the relevant product page on our site. You can also watch our video guide to positioning CO detectors.
Smoke alarms are more likely to ‘chirp’ at night due to lower temperatures.
The voltage of a battery drops as it reaches the end of its life. When a smoke alarm detects this lowered voltage, it emits a regular beeping sound before the battery finally expires, providing sufficient time to replace the battery before the alarm is deactivated.
Lower temperatures can also cause the voltage of a battery to drop. Our houses are often cooler at night, causing the voltage to drop, which triggers the low battery alert. It is particularly common in autumn and winter.
Yes, carbon monoxide alarms are required where a new or replacement fixed combustion appliance is installed.
Owner-occupied homes in England and Wales should follow The Building Regulations Approved Document J for combustion appliances and fuel storage systems. Requirement J3 states that, where a new or replacement fixed combustion appliance is provided, appropriate provision shall be made to detect and give warning of the release of carbon monoxide. Government guidance recommends the use of 'tamper-proof' or 'sealed for life' alarms such as those using lithium batteries, or alternatively mains-powered models which are directly wired into the mains electrical supply as opposed to plug-in types.
Please see our page on carbon monoxide alarm legislation for more specific guidance or view our range of suitable carbon monoxide alarms.
Yes, one carbon monoxide alarm is required in any room used as living accommodation which contains a fixed combustion appliance (excluding gas cookers). Where a new or replacement combustion appliance is installed, the CO alarm must be powered by a sealed lifetime battery or directly wired into the mains electrical supply.
The Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022 applies to all social housing and rental properties in England and Wales and requires working smoke and carbon monoxide (CO) alarms are installed. Specifically for carbon monoxide detectors, this 2022 update expanded existing requirements from just solid fuel burning appliances to include all fuel types. Landlords are required to ensure alarms are present, installed in an effective way to protect occupants, and in working condition at the start of each tenancy. Occupants are responsible for regular testing of alarms and replacing batteries, where applicable, but replacing a faulty or end-of-life alarm is the landlord's responsibility. The rules in Approved Document J must also be followed when a new or replacement combustion appliance is installed, just like for owner-occupied homes.
Please see our page on carbon monoxide alarm legislation for more specific guidance or view our range of suitable carbon monoxide alarms.
Yes, carbon monoxide alarms are required for rented properties in Wales, as explained in The Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022. This applies to all social housing and rental properties in England and Wales and requires working smoke and carbon monoxide (CO) alarms are installed.
Specifically for carbon monoxide detectors, this 2022 update expanded existing requirements from just solid fuel burning appliances to include all fuel types. One carbon monoxide alarm is required in any room used as living accommodation which contains a fixed combustion appliance and, for Wales under the Renting Homes (Fitness for Human Habitation) (Wales) Regulations 2022, this includes gas cookers. Landlords are required to ensure alarms are present, installed in an effective way to protect occupants, and in working condition at the start of each tenancy. Occupants are responsible for regular testing of alarms and replacing batteries, where applicable, but replacing a faulty or end-of-life alarm is the landlord's responsibility. The rules in Approved Document J must also be followed when a new or replacement combustion appliance is installed, just like for owner-occupied homes.
Please see our page on carbon monoxide alarm legislation for more specific guidance or view our ranges of suitable carbon monoxide alarms.
Yes, carbon monoxide alarms are required in homes with fuel-burning appliances. From February 2022, all homes in Scotland – both owner-occupied and rented – must be brought up to a certain minimum standard of smoke alarms and CO alarms. This legislation specifies a common minimum coverage; it does not take precedence over Building Regulations or other specific legislation that may stipulate more alarms are required.
In terms of carbon monoxide specifically, alarms are required in all rooms where there is an appliance of any fuel type (e.g. fireplace, boiler), excluding those solely for cooking, or a flue. All types of alarm must be mains powered (fixed wiring, not a mains plug) or powered by a tamper-proof lifetime battery.
Please see our page on carbon monoxide alarm legislation for more specific guidance or view our ranges of suitable carbon monoxide alarms.
Yes, a sealed battery or mains-powered carbon monoxide alarm must be provided with a new or replacement combustion appliance, excluding those designed solely for cooking purposes. The CO detector should be installed in the same room as the appliance if it is a room normally used by occupants; if it is, for example, a boiler located in a dedicated room / cupboard that occupants do not normally enter, the detector should be located just outside of that cupboard or room.
This has been in effect since 2012, with the guidance in clause 2.51 of The Building Regulations Technical Booklet L setting out requirements for combustion appliances and fuel storage systems.
Please see our page on carbon monoxide alarm legislation for more specific guidance or view our range of suitable carbon monoxide alarms.
Yes, landlords are required to provide CO alarms for their tenants.
Section 8 of The Private Tenancies Act (Northern Ireland) 2022 requires landlords to provide and keep in proper working order 'sufficient appliances' for detecting and giving warning about dangerous levels of carbon monoxide. The original legislation does not specify the power type, quantity, or positioning of alarms, so new legislation effective from September 2024, The Smoke, Heat and Carbon Monoxide Alarms for Private Tenancies Regulations (Northern Ireland) 2024, is being introduced to clarify these aspects. For carbon monoxide requirements in rented properties, the law now specifies that a carbon monoxide alarm should be mains powered (not plugged in) OR powered by sealed batteries that last the full sensor lifespan. The alarms should be fitted in every room which contains a fixed combustion appliance or flue, excluding cooking appliances.
Please see our page on carbon monoxide alarm legislation for more specific guidance or view our range of carbon monoxide alarms.
In short: yes, but there isn't just one, single rule to follow.
Legislative requirements for carbon monoxide alarms vary by which country of the UK your house is in and whether it is rented or owner-occupied. Most legislation requires at least one carbon monoxide alarm is fitted near new or replacement fuel-burning appliances (e.g. boiler, oven, fire place), specifically either 'tamper-proof' / 'sealed for life' alarms such as those using lithium batteries, or alternatively mains-powered models which are directly wired into mains supply as opposed to plug-in types. Some countries have exceptions for fuel-burning appliances used solely for cooking. Rented properties mostly require a CO alarm immediately even if no appliances are being installed or replaced.
Please see our page on carbon monoxide alarm legislation for more specific guidance, links to relevant legislation & government guidance, and links to carbon monoxide alarms suitable for each. Alternatively, please view our full range of carbon monoxide alarms if you already know what type you need.
The symptoms of CO poisoning can range from mild flu-like symptoms such as headache, drowsiness, confusion, nausea and dizziness to more severe symptoms like breathing difficulties and irregular heartbeat. CO poisoning can ultimately lead to coma and death.
View more symptoms on our carbon monoxide information page.
No, normal smoke alarms cannot detect carbon monoxide (CO). Only combined smoke and CO alarms can detect both fire and carbon monoxide gas.
Most legislation advises at least one carbon monoxide alarm is fitted near new or replacement fuel-burning appliances that are fixed installations, though rented properties (both social and private sector) often require CO alarms be provided by landlords even if no appliances are being installed or replaced. Examples include boilers, coal fires, wood burners, and gas ovens and cookers, though an exception is often made in legislation for gas appliances solely used for cooking.
However, any and all materials can give off CO when burning, including gas cookers. Carbon monoxide can also spread from neighbouring properties or outside sources such as vehicle fumes. Because of this, Safelincs strongly recommends the installation of carbon monoxide detectors in every home, and also at head-height in bedrooms to protect occupants while sleeping.
Landlords, please see our pages for English, Welsh, and Scottish alarms or our landlord guidance page for more information.
Carbon monoxide (CO) is a colourless, odourless, tasteless gas that is undetectable by humans. Inhaling CO reduces the blood's ability to carry oxygen to the body's organs and cells.
Each year, over 50 people die in the UK from exposure to carbon monoxide. Many more people die through strokes and respiratory illnesses made worse by inhaling low levels of CO over prolonged periods.
To protect you and your family, purchase a carbon monoxide detector and use the test button weekly to check it is in working order.
Carbon monoxide (CO), also known as The Silent Killer, is created by the incomplete combustion of fossil fuels (gas, oil, coal and wood) used in everyday appliances such as heaters, engines and boilers. CO is undetectable by humans as it is a colourless, odourless and tasteless toxic gas, hence why it is important to have carbon monoxide detectors where incomplete combustion is possible. Humans can experience carbon monoxide poisoning with prolonged exposure to CO, and may experience symptoms ranging from headaches and nausea to coma and death.
Generally, the process for interlinking hardwired alarms is the same. Firstly, you need to make sure that the alarms you are purchasing are compatible with each other, as alarms from different manufacturers (in most cases) do not mix. Dependent on the manufacturer's instructions, you will then be advised to use either a length of bell wire / twin cable to serve as an interlink cable, or 3-core and earth (which is usually adopted in newer installations).
In the same way as interlinking hardwired alarms, it is still crucial to check compatibility between alarms for systems that link wirelessly. The way in which radio-interlinked alarms are connected can differ from brand to brand, however, there will be instructions included with the alarm to guide you through the interlinking process. No signal cables are required between radio-interlinked alarms.
Related videos:
How to radio-interlink the Ei3100RF series smoke alarms
How to radio-interlink the Firehawk W Series smoke and heat alarms
Reviewed: 14/09/2023 (doc:536 V1.0). Our articles are reviewed regularly. However, any changes made to standards or legislation following the review date will not have been considered. Please note that we provide abridged, easy-to-understand guidance. To make detailed decisions about your fire safety provisions, you might require further advice or need to consult the full standards and legislation.
