Smoke Generation

The most widely used test method to generate smoke from materials exposed to heat and flame is known as the National Bureau of Standards (NBS) Smoke Density Chamber under NFPA Standard-258 and ASTM E-662.  This test method and the optical smoke density standard have been referenced by some agencies in spite of the ASTM scope statement that states, “This test is intended for use in research and development and not as a basis for ratings for building code purposes.  At the present time, no basis is provided for predicting the density of smoke that may be generated by the materials upon exposure to heat and flame under fire conditions.”

In the ASTM E-662 test, a 3 inch x 3 inch sample is placed in a closed chamber and is exposed to a radiant heat energy source of 2.5 watts per square centimeter.  Tests may be conducted in a flaming and non-flaming mode.  A light beam is projected vertically through the closed chamber.  The reduction in light transmittance is measured for the duration of the test.  Using the chamber volume, light path, exposed specimen area, and reduction in light transmittance, calculations to determine specific optical density are performed.  The regulatory limit presently applied by a number of agencies is a maximum specific optical density (corrected) of 450 based on tests conducted in the flaming mode.

Data is available to show reasonable reproducibility; however, a correlation has not been established between ratings developed in the chamber and the performance of materials in the real world.

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