scope:

This section of IEC 6956 describes the apparatus, calibration procedures and basic experimental procedures for the determination of the specific optical density of smoke produced by materials exposed vertically to a radiant heat source with or without the application of a pilot flame. The test specimens are of a defined size. The determination of the optical density is carried out in a pressure controlled chamber previously calibrated with reference materials.

This method is applicable to solid, nonmetallic flat test specimens only. It is not suitable for use with nonplanar specimens, e.g. insulated wire and cable, because it is not possible to obtain a homogeneous distribution of heat flux with such products.

This standard does not provide a classification system for the behaviour of materials.

Materials which melt and flow away from the direct impingment of heat flux may not provide reproducible results and this method is not applicable.

Virtually all nonmetallic materials, including those used in electrotechnical products, emit smoke when exposed to heat. Among the hazards associated with fire, smoke causes human and material damage and impairs fire fighting. Consequently, a reduction in the rate of generation of opaque smoke produced by materials/products during a fire reduces damage to equipment, facilitates evacuation of people and emergency services intervention.

WARNING: Appropriate safety measures are to be taken as toxic and harmful effluents may be produced by pyrolysis or combustion of test specimens.