Carbon Monoxide Alarm Requirements for Wales Landlords

Which Rooms Need a CO Alarm

Under Regulation 5 of the Renting Homes (Fitness for Human Habitation) (Wales) Regulations 2022, a carbon monoxide alarm must be present in every room containing a fixed combustion appliance. That includes:

• Gas boilers (even combi boilers in a kitchen cupboard)
• Gas fires and decorative flame-effect fires
• Gas hobs and cookers
• Wood-burning stoves and multi-fuel burners
• Oil-fired heaters

If a room has the appliance, it needs a CO alarm — regardless of whether the room is a living room, kitchen, bedroom, or utility space.

One important exception: appliances owned by the contract-holder are excluded from your inspection duty under the Gas Safety (Installation and Use) Regulations 1998. But you are still responsible for the fixed gas supply pipework and flues those appliances connect to, and a CO alarm in the room protects against leaks from either source.

Battery or Hardwired?

Unlike smoke alarms in Wales — which must be hardwired and interlinked — CO alarms can be powered by a sealed long-life battery or connected to the mains. Both satisfy the regulations, as long as the alarm meets BS EN 50291 and produces an audible warning.

Interlink is not statutorily required for CO alarms, though manufacturers increasingly offer interlinkable models. In a larger property or HMO where a boiler room is distant from bedrooms, interlinking the CO alarm to the smoke detection circuit makes practical sense.

Placement and Positioning

BS EN 50291 recommends mounting the CO alarm at head height on a wall or on the ceiling, between 1 and 3 metres horizontally from the combustion appliance. Avoid placing it directly above the appliance, in a corner where air does not circulate, or near an open window or extractor fan — airflow can dilute CO readings and delay detection.

For a room with more than one combustion appliance (a gas hob and a boiler sharing a kitchen, for example), a single alarm positioned to cover both appliances is acceptable, provided it is within the recommended distance from each.

Sensor Expiry and Replacement

Electrochemical CO sensors degrade over time. Most sealed-battery units have a 7-year sensor life; some premium models last 10 years. After the sensor expires, the alarm will not detect carbon monoxide reliably even if the battery still works.

Check the manufacture date or expiry date printed on the back of the unit. If the sensor has expired, the alarm must be replaced before the next occupation contract begins, and the replacement date should be logged.

Testing at the Start of Each Contract

You must confirm the CO alarm is in proper working order when each occupation contract begins. Press the test button: if the alarm sounds, it is functional. If it does not sound, replace it immediately.

During the contract, routine operational testing (the monthly button press) is typically the contract-holder's responsibility. Replacing defective or expired units remains yours under Section 92 of the Renting Homes (Wales) Act 2016.

What Missing CO Alarms Mean for Your Tenancy

A dwelling without the required CO alarms is automatically unfit for human habitation. For an unfit period, the contract-holder is not liable to pay rent, and rent paid in advance for that period may be recovered as a debt or offset against future rent. A Section 173 possession notice is barred while the relevant statutory requirements remain unmet. An RRO is a separate Welsh remedy for qualifying Rent Smart Wales licensing offences; an alarm breach alone does not create one.

A quality BS EN 50291 sealed-battery CO alarm costs between £15 and £30. The financial exposure from non-compliance is incomparably larger.

The Fitness for Human Habitation compliance guide includes an Alarm Compliance Map that records every alarm's location, type, sensor expiry date, and last test — a single document proving your CO coverage is current.

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