This European Standard specifies general requirements for the construction, testing and performance of electrically operated carbon monoxide gas detection apparatus, designed for continuous operation in domestic premises. The apparatus may be mains or battery powered. Such apparatus is intended to warn of an accumulation of CO, enabling the occupant to react before being exposed to significant risk. This standard specifies two types of apparatus, these are: Type A - to provide a visual and audible alarm and an executive action in the form of an output signal that can be used to actuate directly or indirectly a ventilation or other ancillary device. Type B - to provide a visual and audible alarm only. This standard excludes apparatus: - for the detection of combustible gases, other than carbon monoxide itself; (see EN 50194:2000); - for the detection of CO in industrial installations or commercial premises; (see EN 45544 series); - for use in boats, caravans or mobile homes; - for CO measurement for smoke and fire detection (see prEN 12239).