This technical specification is applicable to flat@ solid non-metallic specimens of materials used in electrotechnical products. This method is not applicable to the testing of non-flat products such as insulated wires and cables@ as it is not possible to obtain a satisfactory distribution of heat flux with such products. This method may not be applicable for materials which melt and flow away from the direct impingement of heat flux and do not give a smoke emission@ which is representative of current knowledge from real fire situations. The purpose of this technical specification is to determine@ under certain specific experimental conditions@ the optical density of smoke produced by materials exposed vertically to a radiant heat source with or without the application of a pilot flame in a closed chamber (i.e. without airchange).