Provides details of the test apparatus to be used for measuring smoke emission when electric or optical fibre cables are burnt under defined conditions, for example, a few cables burnt horizontally. The light transmittance (lt) under flaming combustion and smouldering conditions can be used as a means of comparing different cables or complying with specific requirements. NOTE: For the purposes of this standard, the term ""electric cable"" covers all insulated metallic conductor cables used for the conveyance of energy or signals. The principal changes with respect to the previous edition are as follows: a) closer definition of the draught screen and the chamber orifices; b) closer definition of the support for the cable(s) under test; c) removal of minor differences with equivalent CENELEC work to allow parallel voting with that body. Has the status of a group safety publication in accordance with IEC Guide 104.