Time‐dependent mass loss rate behavior of wall materials under external radiation

External radiation in enclosure fires can significantly enhance flame spread and fire growth. One of the effects of external radiation is to increase the mass loss rate of the fuel, which in turn produces larger flames. In this work, a measurement of mass loss with and without applied radiation was made as a function of time for three types of materials: a plastic (polymethylmethacrylate), wood‐based products (particle board and hardboard), and a paper‐based product (cardboard). The levels of applied radiation ranged from 0 to nearly 12 kWm⁻². The purpose of the investigation was to (1) quantitatively determine the effect of external radiation on the mass loss of various materials,(2) measure various parameters which may be used to characterize the mass loss rate history of the materials and (3) determine a method for expressing the mass loss rate as a function of time for input into numerical models. Higher levels of external radiation resulted in higher peak mass loss rates and quicker consumption of the material. Quantities which are useful for ranking the flammability of materials have been measured for the samples tested and are tabulated.