This part of ISO 7240 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. NOTE The term “optical” is used to describe that part of the electromagnetic spectrum produced by the transmitter to which the receiver is responsive; this is not restricted to visible wavelengths.