The Legal Requirement for Carbon Monoxide Alarms

Since 1 October 2022, the Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022 require all private in England to install a carbon monoxide alarm in every room that contains a fixed combustion appliance — including gas boilers, gas fires, open fires and wood-burning stoves. This is a legal requirement that must comply with from the start of any tenancy. Failure to comply can result in a remedial notice from the local authority and a civil penalty of up to £5,000.

Which Rooms Need a CO Alarm?

A carbon monoxide alarm is required in any room containing a fixed combustion appliance. This includes:

Any room with a gas boiler (including a boiler cupboard or utility room)
Any room with a gas fire or decorative gas flame effect fire
Any room with an open fire or wood-burning stove
Any room with an oil-fired boiler or appliance

Note: Gas cookers and gas hobs are specifically excluded from the regulation — you do not legally need a CO alarm in the kitchen if the only gas appliance is a cooker or hob. However, it is good practice to install one regardless.

Where to Place CO Alarms

For maximum effectiveness, carbon monoxide alarms should be positioned as follows:

At head height when sleeping — CO is approximately the same density as air, so ceiling height positioning is not as critical as for smoke alarms
Within 1–3 metres of any potential CO source (boiler, gas fire)
Away from corners and areas with poor air circulation
In a location where the alarm can be heard from any sleeping area
Not directly above or beside a cooker, or in areas of high humidity

Types of CO Alarm

There are two main types of carbon monoxide alarm:

Battery-operated alarms — easy to install, no wiring required. Batteries typically last 5–7 years on the alarm itself (sealed battery units). Replace the entire unit when the battery life ends.
Mains-powered alarms with battery backup — more reliable, always powered, but require electrical installation. Recommended for new builds and major refurbishments.

Look for alarms that comply with BS EN 50291-1 and carry the BSI kitemark. These are the recognised standards for domestic CO alarms in the UK.

Testing and Maintenance

Test the alarm monthly using the test button
Replace battery-only alarms as recommended by the manufacturer (typically every 7–10 years)
Keep the alarm clean and free from dust — vacuum around the sensor annually
Never paint or cover a CO alarm
Replace immediately if the alarm shows a fault indicator

What to Do If the Alarm Sounds

If your carbon monoxide alarm activates:

Do not ignore it — evacuate all occupants from the building immediately
Do not go back inside until declared safe by the emergency services
Call 999 if anyone is feeling unwell — CO poisoning symptoms include headaches, nausea, dizziness and confusion
Call the National Gas Emergency Line on 0800 111 999 if you suspect a gas appliance is the source
Seek medical attention even if symptoms seem mild — CO poisoning can be delayed in onset

CO Poisoning Warning: Carbon monoxide is odourless, colourless and tasteless. You cannot detect it without an alarm. Over 50 people die from accidental CO poisoning in the UK every year, and hundreds more are seriously injured. A CO alarm is the only reliable way to detect this silent killer.

Annual Gas Safety Certificate

An annual gas safety inspection by our Gas Safe registered engineers is the best way to prevent CO risks from gas appliances. Includes combustion analysis to detect incomplete combustion. From £49 inc VAT.

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Why Carbon Monoxide Alarms Are Critical

Carbon monoxide (CO) is produced when gas appliances do not burn fuel completely. Because CO is colourless and odourless, it cannot be detected by human senses alone. According to Public Health England, CO poisoning is responsible for approximately 40 deaths per year in England and Wales from accidental non-fire-related exposure, and hundreds more hospital admissions. The vast majority of incidents are preventable with a functioning CO alarm.

CO Poisoning Symptoms and Concentration Levels

CO Level (ppm)Effect on Healthy Adult

35 ppmHeadache after 6–8 hours of continuous exposure

100 ppmHeadache after 2–3 hours

200 ppmHeadache, dizziness and nausea after 2 hours

400 ppmLife-threatening after 3 hours

800 ppmDeath within 2–3 hours

6,400 ppmDeath within 10–15 minutes

If your CO alarm sounds: Get everyone out immediately. Do not go back in. Call 999. Call the National Gas Emergency Service on 0800 111 999. Do not re-enter until emergency services say it is safe.

CO Alarm Legislation for (England)

The Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022 (in force from 1 October 2022) require all private sector to install a CO alarm in every room used as living accommodation that contains a fixed combustion appliance (boiler, gas fire, gas cooker). Alarms must be in working order on the first day of every new tenancy. Penalty for non-compliance: fine up to £5,000.

Where to Install CO Alarms

Room / LocationCO Alarm Required?

Room containing boiler✅ Yes — mandatory (England)

Room with gas fire✅ Yes — mandatory (England)

Kitchen with gas cooker (living space)✅ Yes — mandatory (England)

Bedroom adjacent to boiler room⚠️ Strongly recommended

Garage or utility with gas appliances⚠️ Strongly recommended

CO Alarm Placement Guidelines

Height: CO is approximately the same weight as air, so alarms can be mounted at head height or on the ceiling.
Distance from appliance: Position alarms at least 1–3 metres from the gas appliance to avoid false alarms.
Avoid: Placing alarms behind curtains, in dead air spaces, or in areas of high humidity (bathrooms).
Multiple floors: One alarm per floor with a gas appliance is the minimum; one per room with an appliance is best practice.

CO Alarm Types and Standards

All CO alarms used in rented properties must meet BS EN 50291. Recommended types:

Electrochemical sensor alarms
Most accurate, 5–7 year lifespan. Brands: Kidde, FireAngel, Aico, BRK.

Combination CO + smoke alarms
Combines smoke and CO detection. Brands: Kidde 2-in-1, Aico Ei3028.

Mains-powered (AC) alarms
Hard-wired with battery backup. Ideal for HMOs. More reliable long-term.

Interconnected wireless alarms
When one alarm triggers, all alarms sound. Essential for larger properties.

CO Alarm Lifespan and Replacement

CO alarms have a finite lifespan — typically 7–10 years. After this period, the electrochemical sensor degrades and the alarm may not respond to CO. Check the back of the alarm for the manufacture date and replace before the recommended end date.

Book Your Annual Gas Safety Certificate

Our engineers check CO alarms are present and correctly sited at every gas safety inspection. CP12 from £49 inc VAT.

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Frequently Asked Questions — CO Alarms

Do I need a CO alarm if the boiler is in a cupboard?

Yes. If the boiler is in a cupboard within a room used as living accommodation, a CO alarm is required in that room. CO can escape from the boiler cupboard and accumulate in the room.

Does my tenant need to test the CO alarm?

You (the ) must test the alarm on the first day of each new tenancy. After that, tenants take on day-to-day responsibility for checking the alarm — they should test it monthly by pressing the test button.

Can I use a CO detector with a digital readout?

No. The regulations require an audible alarm. A digital readout device alone is not compliant for purposes, though it may be useful as an additional monitoring tool.

What is the penalty for not having a CO alarm?

The local housing authority can impose a fine of up to £5,000 for failure to install a CO alarm as required under the Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022.

Carbon Monoxide Alarm Guide — Legal Requirements for London