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.Additional requirements for apparatus to be used in recreational vehicles and similar premises are specified in EN 50291-2.NOTE For caravan holiday homes EN 50291-1 applies.This European Standard specifies two types of apparatus, these are• type A – to provide a