Carbon Monoxide Alarm Requirements for Landlords UK 2026

The 2022 Regulations extended and strengthened the 2015 regime. Before October 2022, CO alarms were only required in rooms with solid-fuel burning appliances such as wood burners, log burners, and open coal fires. From October 2022, the duty expanded to cover all fixed combustion appliances — including gas boilers, gas fires, and oil-fired central heating boilers — in any room used as living accommodation.

Carbon monoxide is colourless and odourless. Exposure causes headaches, dizziness, and confusion, and at high concentrations is rapidly fatal. Properties with older gas appliances, poorly maintained flues, or blocked ventilation are at particular risk. For landlords, CO alarm compliance is not only a legal duty but a critical safeguard against tenant harm and the reputational and legal consequences that follow a CO incident.

Which rooms require a carbon monoxide alarm?

The duty applies to any room used as living accommodation that contains a fixed combustion appliance. This includes:

Any room with a gas boiler (including combi boilers and system boilers) where the room is used for living or sleeping
Any room with a gas fire, gas log-effect fire, or decorative gas appliance
Any room with an oil-fired boiler or oil-fired heater
Any room with a solid-fuel burning appliance including wood burners, log burners, multi-fuel stoves, and open fires burning coal, wood, or peat
Utility rooms or plant rooms that are also used as living accommodation (rare but possible in some converted properties)
Importantly, gas cookers are specifically excluded from the duty — a kitchen with only a gas hob and no boiler or gas fire does not trigger the CO alarm requirement

What standard must the alarm meet?

CO alarms installed to satisfy the Regulations must:

Conform to BS EN 50291-1 (electrochemical cell alarms, the most common domestic type) or BS EN 50291-2 (combined alarm/display units). Check the product box or instructions for the standard reference before purchasing
Be audible throughout the property when activated — the alarm must be capable of being heard from every room
Have a display showing the CO concentration reading, or a visual indicator — audible-only units that pre-date the 2022 revision of BS EN 50291 may not comply with the latest standard
Have a battery backup or mains power with battery backup. Mains-only units with no battery are not compliant
Not be past their replacement date. Most CO alarms have a sensor life of 7-10 years. A sticker on the unit usually states when it expires. Replace before expiry — an expired alarm may fail silently
Be positioned at approximately head height, or in accordance with manufacturer instructions. Avoid placing alarms directly next to the appliance, above cooking areas, or in high humidity zones

Testing and tenancy start duties

The Regulations impose specific duties around tenancy commencement:

Test on day one: the landlord (or agent) must test the CO alarm on the first day of a new tenancy. Most modern alarms have a test button — press and hold until the alarm sounds. Document this in writing
Pre-tenancy check: before the tenant moves in, confirm all CO alarms are in working order. Replace batteries if low. If the unit has expired, replace it entirely
Reporting and repair: if a tenant reports a faulty or non-functioning CO alarm during a tenancy, the landlord must repair or replace it as soon as reasonably practicable. Failure to do so once notified is a distinct breach
Check records: keep a written record of pre-tenancy alarm tests, ideally signed by the tenant on the inventory or in the tenancy agreement itself. This protects against enforcement action
Periodic inspection: although the Regulations only require testing at tenancy start, prudent landlords test CO alarms annually (for example, during the annual gas safety check visit) and record the result

Enforcement and penalties

Local housing authorities (district and borough councils) are responsible for enforcing the CO and smoke alarm Regulations:

Remedial notice: if a local authority determines a landlord has breached the Regulations, it may serve a remedial notice requiring the breach to be remedied within 28 days
£5,000 fine: if the landlord fails to comply with the remedial notice, the local authority may carry out the remedial action itself and impose a civil penalty of up to £5,000
No criminal record: the penalty is a civil (not criminal) charge but is recorded and can affect future licensing applications and landlord reputation
Tenant complaints: tenants can report missing or non-functional alarms to the local authority, which may trigger an inspection under the Housing Health and Safety Rating System (HHSRS) as well as the alarm Regulations
Interplay with Gas Safety: the Gas Safety (Installation and Use) Regulations 1998 require annual gas safety checks by a Gas Safe registered engineer. The engineer will usually note the presence of CO alarms on the certificate — a missing alarm can prompt a proactive referral to the local authority

CO alarms vs gas safety checks: how they work together

CO alarms and annual gas safety certificates address different risks and both are mandatory:

Gas safety certificate (CP12): an annual check by a Gas Safe registered engineer of all gas appliances, flues, and pipework. It tests whether appliances are operating safely and not emitting dangerous CO levels
CO alarm: a continuous monitoring device that alerts occupants if CO builds up in the room, for example due to a boiler flue becoming blocked, a cracked heat exchanger, or an incomplete combustion event between annual inspections
Both are required: a passed gas safety certificate does not substitute for a CO alarm. A CO alarm does not substitute for a gas safety check. They address different failure modes
Engineer feedback: Gas Safe engineers will often note during a service visit if a CO alarm is absent, expired, or not working, though they have no direct legal duty to enforce the alarm Regulations — that sits with the local authority
EICR interactions: an Electrical Installation Condition Report (EICR) checks the electrical installation but not CO alarms directly. However, if CO alarms are hardwired (mains-connected), the EICR assessment covers the electrical supply to the alarm

Practical compliance steps for landlords

Implement a simple CO alarm compliance system:

Audit every property: for each property, identify every room with a fixed combustion appliance (gas boiler, gas fire, oil boiler, solid fuel stove). Map which rooms require an alarm
Check installed alarms: verify that each existing alarm conforms to BS EN 50291, is within its sensor lifespan, has working batteries, and is audible from adjacent rooms
Replace outdated units: CO alarms purchased before the 2022 Regulations may not meet the updated BS EN 50291 standard. Replace systematically if unsure
Update your check-in process: add a CO alarm test to your pre-tenancy checklist. Record the test in the inventory and have the tenant acknowledge it on the tenancy agreement or a separate receipt
Include in periodic inspection schedule: test and record CO alarm status at every property inspection (typically every 3-6 months) and at each annual gas safety visit
Keep spare alarms: hold a supply of compliant replacement alarms so that a fault reported mid-tenancy can be remedied on the same day rather than waiting for delivery

Frequently asked questions

Do I need a CO alarm if I only have a gas boiler in a cupboard, not a habitable room?+

The duty applies to rooms used as living accommodation that contain a fixed combustion appliance. A boiler housed entirely in a dedicated cupboard or plant room that is not itself used as living accommodation does not strictly require a CO alarm under the Regulations. However, because CO can migrate from the cupboard into adjacent living spaces, best practice — and the guidance from the Government and Health and Safety Executive — is to install an alarm in the nearest habitable room anyway. Many landlords install an alarm both in the boiler cupboard and the adjacent hallway or kitchen as a belt-and-braces approach.

Can I use a combined smoke and CO alarm?+

Yes. Combined smoke and CO alarm units are available and can satisfy both the smoke alarm duty (requiring alarms on each storey and in rooms used as living accommodation) and the CO alarm duty (rooms with combustion appliances), provided the unit is rated to both BS 5446-2 (smoke) and BS EN 50291 (CO). Check the product specification carefully — some combined units meet one standard but not the other. Separate dedicated alarms for smoke and CO are often preferable as they can be positioned optimally for each hazard.

Does the CO alarm duty apply to HMOs?+

Yes. The Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022 apply to all private residential lettings in England, including HMOs of all sizes. For HMOs, the duty is in addition to the HMO Management Regulations 2006, which impose broader fire safety and general safety duties. Each room used as living accommodation that contains a combustion appliance requires a CO alarm. In an HMO with a gas boiler in a shared kitchen, the kitchen requires a CO alarm even if the boiler is in a cupboard within the kitchen.

Does the rule apply to properties in Wales, Scotland, and Northern Ireland?+

The Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022 apply to England only. Wales has separate legislation under the Renting Homes (Fitness for Human Habitation) (Wales) Regulations 2022, which also require CO alarms in rooms with combustion appliances. Scotland's regulations (Housing (Scotland) Act 2006 provisions as amended) require interlinked smoke and heat alarms plus a CO alarm where there is a fuel-burning appliance. Northern Ireland has different requirements. Always check jurisdiction-specific rules for properties outside England.