The alarm should comply with BS 50291-1:2018, be provided in the room where the appliance is located and be powered by a battery designed to operate for the working life of the alarm, it should also incorporate a warning device to alert users when the working life of the alarm is about to expire.
As an alternative, a mains- powered alarm with fixed wiring (not a plug-in type) conforming to BS EN 50291 of the Type A type may be used, providing they are fitted with a sensor failure warning device.
Further guidance and recommendations on the installation of carbon monoxide alarms are available in BS EN 50292:2013 and from manufacturers’ instructions.
Building Regulations Approved Document J