Fire-extinguishing effectiveness of new binary agents

Abstract

The search for a new fire-extinguishing agent with all the desirable properties of halon 1301 has not been successful. During the last few years, several chemical groups with very low extinguishing concentrations have been identified. Most of these compounds have high boiling points and are not suitable replacements for halon 1301. However, mixtures of these chemicals in an inert gas could produce fire-extinguishing agents with many of the desirable properties of halon 1301. To study binary fire suppressants, one has to determine the extinguishing concentrations for several compositions of a given chemical in an inert gas. This process is expensive and time consuming. A method to estimate the extinguishing concentrations would be helpful in reducing the number of experiments needed for any binary system. In this study, a method based on adiabatic flame temperature calculations and the dependence of the rate of fire suppression of chemical agents on temperature was used to estimate the extinguishing concentration of binary mixtures. The method was tested for five organic compound/nitrogen mixtures. Five compounds that have been shown to have very low extinguishing concentrations and very short atmospheric lifetime were selected for this study. Cup burner experiments were conducted for several concentrations of each chemical in nitrogen. All the five binary systems showed synergism. As expected, the degree of synergism was highest at low concentrations of the chemical. For each binary system, extinguishing concentrations of the pure compounds and one binary data were used to predict the extinguishing concentrations for the entire range of binary composition. The predicted values are very close to experimental data.