CO alarm rules for properties across the UK

This article sets out the requirements for CO alarms in both rented and owned properties in England, Wales, Scotland and Northern Ireland. These requirements cover CO alarms in all rented homes and when boilers are installed in new and existing homes, both owned and rented. The key elements are:

  • CO alarms are mandatory in rooms with any fixed-combustion appliance (excluding gas cookers) in privately rented homes and social housing
  • CO alarms are also mandatory when any fixed combustion appliance is installed or replaced, excluding gas cookers, in all homes.
  • Smoke alarms are mandatory in all social housing. This was already a requirement in privately rented homes.

These requirements are set out in the updated edition of Approved Document J: Combustion appliances and fuel storage systems, which came into effect on 1 October 2022.

The Approved Document also sets out guidance on the types of CO alarm to be fitted:

  • They should comply with BS EN 50291
  • They should powered by a battery designed to operate for their working life and be able to alert users when this is coming to its end
  • Alternatively, a mains-powered alarm with fixed wiring (not plug-in) should be fitted, provided that the alarm has a sensor failure warning device. Alarms should have an output function for triggering ancillary devices such as remote alarms or specialist alarms for older people and those with disabilities.

The CO alarm should be located in the same room as the combustion appliance and on the ceiling at least 300mm from any wall, or on a wall as high up as possible (above any doors and windows) but not within 150mm of the ceiling. The alarm should be sited between 1m and 3m horizontally from the appliance.

The government has published guidance supporting the requirements for smoke and CO alarms in all rented homes, and for CO alarms when boilers are installed in new and existing homes, irrespective of tenure.

The regulations in other UK nations

  • Wales: In rental properties, each room that contains a gas appliance, an oil-fired combustion appliance or a solid fuel burning combustion appliance must have a working CO alarm. The regulations also apply to rooms containing gas cookers. These rules are due to be updated on 1 December.
  • Scotland: In all homes, rooms that contain a carbon-fuelled appliance must also contain a CO alarm. If the alarm is battery-operated, it should be a sealed unit for the duration of it its life. Rooms containing appliances used solely for cooking are exempt.
  • Northern Ireland: Carbon monoxide alarms are mandatory in all homes in the room where a new or replacement combustion appliance not designed solely for cooking purposes has been installed.


Who will fit CO alarms?
Fitting CO alarms upon the installation of new and replacement fixed-combustion appliances in existing dwellings will most likely be carried out by Gas Safe registered engineers or those working within a Building Regulations competent person scheme. Compliance of the work with the requirements of the Building Regulations 2010 is self-certificated.

I’m carrying out a LGSR check and there is no CO alarm. What should I do?
If you identify a situation where there should be a CO alarm but there isn’t one, you should notify the responsible person and record it on your paperwork. This is not a legal requirement but it is the responsible thing to do as a gas engineer.

Is the lack of a CO alarm an unsafe situation?
No. The rules that apply to the requirements for CO alarms are not gas regulations. It is not an unsafe situation and does not require any action under the Gas Safety Regulations.

Are specialist alarms required for people with disabilities?
Landlords should make an informed decision and choose the best alarms for their properties and tenants, with due regard for their residents’ circumstances. For example, specialist smoke alarms and carbon monoxide alarms that alert by vibration or flashing lights (as opposed to by sound alerts) may be required for residents who are deaf or hard of hearing. Landlords should consider their duties under the Equality Act 2010.

How are these regulations enforced?
For rented properties, the regulations will be enforced by local authorities.

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