Fire Safety Science Digital Archive

Results are presented which show the effect of fire retardant addition on the fuel related properties used in diffusion flame calculations. Samples of cellulose retarded with up to 3 wt. percent of sodium hydroxide were subjected to a radiant heat flux of 40 kWm² in a special apparatus designed for this purpose. The volatile products of pyrolysis were analyzed using a gas chromatograph to determine the concentration of inert gases (carbon dioxide and water). Retardant addition was found to increase both the char yield and the production of inert gases. This results in a decrease in the fuel fraction in the pyrolysate from 69 wt. percent for pure cellulose to 35 wt. percent for retarded cellulose. The corresponding change in the stoichiometric oxygen/fuel ratio is from 1.6 for pure cellulose to a maximum of 2.3 for retarded cellulose. Retardant addition also causes a decrease in the heat of gasification (defined as the energy input to generate a unit mass of volatiles) and an increase in the heat of combustion of the combustible gases in the pyrolysate.