Flame Inhibition by CF3CHCl2(HCFC-123)

A kinetic model is suggested for hydrocarbon/air flame propagation with addition of hydrochloroflurocarbon (HCFC) fire suppressant, encompassing the combined chemistry of fluorine- and chlorine-containing species. Calculated burning velocities using the kinetic model are in good agreement with available experimental burning velocity data for CF3Cl, CF2Cl2, or CFCl3 added to CO/H2/O2/Ar flames. The agent CF3CHCl2 is more effective than C2HF5, and reaction pathway analysis shows that the inhibition effect of chlorine reactions is greater than that of fluorine. The main reactions of the chlorine inhibition cycle are H+HCl=H2+Cl, OH+HCl=H2O+Cl, Cl+CH4=HCl+CH3, Cl+HCO=HCl+CO, and Cl+CH2O=HCl+HCO. The inhibition effect of CF3CHCl2 is largely the result of competing reactions of chlorine-containing species with hydrogen (and other radical pool) species, decreasing the rate of the chain-branching reaction H+O2, with additional effects from substitution of the reactive chain-branching radicals for less reactive fluorine- and chlorine-containing radicals.