Fire Safety Science Digital Archive

Recently Hottel, Williams and Steward and Atallah have described small-scale experiments on the spread of fire that were made with a view to comparing the results with an appropriate theoretical model of fire spread. Hottel et al supplemented the heat supply to the layers of torn paper or card which constituted the fuel by adding varying amounts of radiation to the heat supplied by the fuel already burning. The effect of this was to increase the rate of spread. Atallah, on the other hand, studied the horizontal spread of fire along sheets of papers of various thicknesses and gave a theory for this based on the assumption that the major source of heating was the radiation from the flames. Hottel et al attempted to allow for convection from the flame as well as the radiation; in their case the major source of heat was usually the supplementary radiation. Earlier work by Stott had shown that flames spread across paper at a roughly constant mass rate of burning so that the lineal rate of spread was inversely proportional to the paper thickness. Simms and Law have analysed Stott's data which corresponds to a burning rate per unit width of fire front of m' = 3.5 mg cm^-1 s^-1 Atallah presented his results in terms of parameters which included the flame height. This was not reported separately but in one example he took a value of l in which is similar to the values recorded by Stott. Using this value, Atallah's data correspond to a burning rate of m' = 5.6 mg cm^-1 s^-1 i.e. of the same order as Stott's.