This European Standard specifies requirements, test methods and performance criteria for line smoke detectors utilising the attenuation and/or changes in attenuation of an optical beam, for use in fire detection systems installed in buildings. This European Standard does not cover: Line smoke detectors designed to operate with separations between opposed components of less than 1 m; line smoke detectors whose optical path length is defined or adjusted by an integral mechanical connection; Line smoke detectors with special characteristics, which cannot be assessed by the test methods in this European Standard. 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.