Carbon Monoxide Alarm UK Regulations 2026 — Landlord Requirements

The Smoke and Carbon Monoxide Alarm (England) Regulations 2015 came into force on 1 October 2015. The original wording required CO alarms in any room used wholly or partly as living accommodation that contained a solid-fuel-burning combustion appliance. Gas-only properties were outside scope.

The 2022 Amendment — formally the Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022 — came into force on 1 October 2022 and substantially extended the CO requirement. From that date, a CO alarm is required in any room used as living accommodation that contains any fixed combustion appliance, including gas, oil and biomass appliances. Gas cookers remained excluded because they are not fixed appliances in the regulatory sense.

The amendment also extended the smoke alarm requirement to social rented housing on the same basis as private rented housing — at least one smoke alarm on every storey containing a room used wholly or partly as living accommodation. Local authority enforcement powers were strengthened with a faster Improvement Notice route.

For London landlords as of June 2026, the position is settled: CO alarms in every room with a fixed combustion appliance, smoke alarms on every storey, both tested and confirmed working at every tenancy start.

A CO alarm is required in every room that meets both of these tests: the room is used wholly or partly as living accommodation, and the room contains a fixed combustion appliance. Both tests must be satisfied — a boiler in an external cupboard is outside scope because the cupboard is not living accommodation.

Common rooms requiring CO alarms: kitchens with a gas boiler or oil boiler installed inside the kitchen; living rooms with a gas fire or solid-fuel stove; bedrooms with a gas fire or back boiler; hallways or under-stairs cupboards only if they double as a usable living space (rare).

Common rooms exempt: bathrooms (steam interferes with sensors and the room is not normally occupied during cooking or heating operation); kitchens with electric-only cooking and a boiler in an external cupboard; rooms with a gas cooker but no boiler or fire — the regulations explicitly exclude cookers from the fixed-appliance definition.

BS EN 50292 governs the siting of domestic CO alarms. The default position is 1-3m horizontally from the combustion appliance, mounted at the height specified by the alarm manufacturer (typically ceiling-mounted or high on the wall above eye level).

Where ceiling mounting is used, the alarm should be at least 300mm from any wall or light fitting. Where wall mounting is used, the alarm should be at least 150mm from the ceiling and at least 1.5m above floor level. Avoid mounting directly above the boiler or fire — the heat plume can damage the sensor and the alarm will misread.

Avoid mounting near windows, doors, ventilation grilles or extraction fans — these draw fresh air past the sensor and dilute any CO concentration, delaying detection. Avoid bathrooms and shower rooms because humidity damages the sensor.

Where the appliance is in a hallway, the alarm goes in the hallway near the appliance. Where the appliance is in the same room as a sleeping occupant — a back boiler in a bedroom, for example — the alarm goes in that bedroom, not in the hallway outside.

Unlike smoke alarms in rented HMOs, CO alarms can be battery-only on a rented property and remain compliant. The Regulations do not specify mains-powered CO alarms. The choice between battery-only and mains-powered comes down to maintenance preference and installation cost.

Battery-only sealed 10-year lithium alarms are now the standard choice. They cost £35-£50 supplied, install in five minutes, and require no maintenance until end of life. The Aico Ei208W and the Kidde 10Y29 are typical Grade D-equivalent units.

Mains-powered CO alarms are typically specified where the smoke alarm system is also mains-powered and there is appetite for a single integrated installation. Aico's Ei208WRF for example pairs with the Ei3000 smoke alarm range over the same RF link, giving the landlord a single coordinated system across smoke, heat and CO detection.

10-year sealed battery CO alarms became the default install in London around 2020. The technology was driven by tenant tampering with replaceable batteries — landlords were finding that 9V backup batteries had been removed within months of installation, often by tenants silencing low-battery chirps.

Sealed batteries cannot be removed. The alarm operates for 10 years from manufacture, then signals end of life via a continuous chirp pattern and is replaced as a complete unit. The total cost of ownership over 10 years is similar to or lower than replaceable-battery models when tampering and re-test labour are included.

All major UK CO alarm manufacturers — Aico, Kidde, FireAngel, Honeywell — now offer 10-year sealed models. The 2022 amendment did not formally require sealed batteries, but it tightened the alarm test obligation on landlords and made tampering-resistance commercially attractive.

The Regulations require the landlord to ensure each alarm is in proper working order at the start of every new tenancy. A simple test-button check satisfies this. The landlord or agent must record the test in writing and retain the record.

During the tenancy, the testing duty shifts to the tenant for routine functional checks. The landlord retains responsibility for replacing any alarm that fails or reaches end of life.

Our tenancy-start checklist runs through the property room by room: smoke alarm on every storey (test, log), CO alarm in every room with a fixed combustion appliance (test, log), confirmation of model and end-of-life date for each alarm, signed compliance certificate to the landlord and a copy to the tenant.

The tenancy-start documentation has become standard evidence in any council inspection or possession dispute under the Renters' Rights Act 2026. Failure to provide it is treated as a presumption of non-compliance.

Modern sealed CO alarms operate for 10 years from the manufacture date. End of life is signalled by a continuous chirp pattern that is intentionally annoying — the alarm cannot be reset and must be replaced. The 10-year clock starts at manufacture, not at installation, so checking the manufacturer date on the back of any inherited alarm is the first audit step on a tenancy turnover.

Battery-replaceable CO alarms — older models from before the 10-year sealed era — typically require battery replacement annually with a full unit replacement at 5-7 years depending on sensor type. These are still in service in some older London rental stock and we routinely flag them for replacement at any compliance audit.

End-of-life replacement of CO alarms is the landlord's responsibility under the 2015 Regulations as amended. The tenant cannot be expected to identify the end-of-life chirp pattern or to source a compliant replacement. Annual or tenancy-turnover audit by the landlord or agent is the practical solution.

The 2015 Regulations as amended provide a Civil Penalty regime for breach. The penalty can be up to £5,000 per breach per property issued by the local council without court process. The breach is each missing alarm — a 3-bed flat with no smoke alarm on the ground floor and no CO alarm in a gas-boiler kitchen is two breaches and potentially £10,000.

Where a fatal CO incident occurs in a non-compliant property, the case routes through the Regulatory Reform (Fire Safety) Order 2005 and corporate manslaughter provisions. The responsible person can face unlimited fines and custodial sentences. We have seen prosecutions concluded against landlords where the missing alarm was the proximate cause of death.

Insurance is invalidated by alarm non-compliance in most policies. A CO-related claim against a non-compliant property is typically refused outright — the landlord absorbs the full loss including any third-party injury claim.

The Renters' Rights Act 2026 added alarm compliance to the precondition list for Section 8 possession claims. A landlord trying to evict a non-paying tenant cannot proceed if the property's alarm coverage is non-compliant — the tenant's defence will raise it as a counter-claim and the court will pause the possession until compliance is achieved.

Our standard CO alarm package for a London rental property includes site survey, model selection, installation, button-test, manufacturer registration and a written compliance certificate. The package costs £85 per alarm fully installed and includes the 10-year sealed unit.

For HMOs and converted blocks we combine the CO retrofit with the BS 5839-6 smoke alarm install and the FRA in a single compliance visit. Bundle pricing reduces the per-unit cost meaningfully and produces a single coordinated certification pack ready for council submission.

Documentation matters as much as the install. We supply every CO alarm install with a one-page certificate listing model, serial number, install date, end-of-life date and the test result. The certificate is digitally signed and attached to the property's compliance file in our portal — accessible to the landlord, agent or council on demand.