1.1 This part of ISO 5659 specifies a method of measuring smoke production from the exposed surface of specimens of essentially flat materials, composites or assemblies not exceeding 25 mm in thickness when placed in a horizontal orientation and subjected to specified levels of thermal irradiance in a closed cabinet with or without the application of a pilot flame. This method of test is applicable to all plastics and may also be used for the evaluation of other materials (e.g. rubbers, textile-coverings, painted surfaces, wood and other materials). 1.2 It is intended that the values of optical density determined by this test be taken as specific to the specimen or assembly material in the form and thickness tested, and are not to be considered inherent, fundamental, properties. 1.3 The test is intended primarily for use in research and development and in fire safety engineering of buildings, trains, ships, etc., and not as a basis for ratings for building codes or other purposes. No basis is provided for predicting the density of smoke that may be generated by the materials upon exposure to heat and flame under other (actual) exposure conditions, nor is any correlation established with measurements derived from other test methods. This test procedure excludes the effect of irritants on the eye. NOTE This test procedure addresses the loss of visibility due to smoke density, which generally is not related to irritancy potency, as explained in Part 1 of this International Standard. 1.4 It is emphasized that smoke production from a material varies according to the irradiance level to which the specimen is exposed. In making use of the results of this method, it should be borne in mind that the results are based on exposure to the specific irradiance levels of 25 kW/m2 and 50 kW/m2.