ISO 7240-12 specifies requirements, test methods and performance criteria for line type smoke detectors for use in fire detection systems installed in buildings. The detectors consist of at least a transmitter and a receiver and can include reflector(s), for the detection of smoke by the attenuation and/or changes in attenuation of an optical beam. This part of ISO 7240 does not cover line-type smoke detectors designed to operate with separations between opposed components of less than 1 m; line-type smoke detectors whose optical path length is defined or adjusted by an integral mechanical connection; line-type smoke detectors with special characteristics, which cannot be assessed by the test methods in this part of ISO 7240.