ISO 5659-2: Smoke generation – Optical density by a single-chamber test

ISO 5659-2 outlines the procedure for measuring the optical density of smoke produced by a material placed in a closed test cabinet and exposed to thermal radiation. The standard was originally developed for plastics, but it can be applied to a range of other products and materials.

In the test, representative specimens of the material are mounted horizontally in a test chamber, and their upper surface is exposed to a specified level of thermal irradiance (usually 25 kW/m² or 50 kW/m²), with or without a pilot flame. The resulting smoke is collected and its optical density is measured using a photometric method.

Some of the key parameters measured include the maximum specific optical density (D_s,max), the specific optical densities at specified times (D_s(1,5), D_s(4), D_s(10)), and the cumulative specific optical densities during the first 4 minutes of the test (VOF₄). A toxicity measurement can also be included to measure toxic gas emissions. Its results are reported as the conventional index of toxicity (CIT_G).

The ISO 5659-2 smoke production test is often required as part of the EN 45545-2 fire safety evaluation of railway materials.