This document serves as a guide on the selection, installation, use and maintenance of apparatus for the detection of carbon monoxide, intended for continuous operation in a fixed installation in domestic premises, caravans and boats. This guide is intended to cover any type of domestic or residential accommodation, including leisure accommodation vehicles such as touring and static caravans, and motor homes; and recreational craft such as canal barges. Some static caravans are used as permanent dwellings, in such cases EN 50291-1 is appropriate. For all other types of caravan, EN 50291-2 is appropriate. This guide is read in conjunction with EN 50291-1 and EN 50291-2 together with any additional relevant national or local regulations. This document refers to the installation of two types of apparatus: a) Type A apparatus, 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; b) Type B apparatus, to provide a visual and audible alarm only. This document excludes apparatus for the detection of combustible gases (see EN 50244) and for industrial installations or commercial premises.