Experimental study of thermal breakdown products from halogenated extinguishing agents

Thermal breakdown products from four different fire extinguishing agents have been analysed. The agents studied were: bromotrifluoromethane (Halon 1301), pentafluoroethane (HFC 125), heptafluoropropane (HFC 227ea) and dodecafluoro-2-methyl-pentane-3-one (C6F-ketone). In the tests, the studied agent was introduced into a propane flame in a diffusion flame burner. The combustion products were analysed using both conventional IR-techniques and FTIR. It could be concluded that for all four extinguishing agents that the extinguishing agent takes part in the combustion process resulting in production of CO and CO2, which was also confirmed by the increase in smoke production with increasing amounts of agent introduced into the flame. Production of HF and COF2 was found in experiments with all four extinguishing agents. In experiments with Halon 1301, the production of HBr was also determined. It was found that the main fraction of fluorine ends up as HF for HFC 227ea and HFC 125 at lower relative application rates. When approaching extinguishing concentrations, the fraction recovered as COF2 increases, but the total recovery of fluorine, including HF and the remaining part of the fluorine, is found in various organic breakdown products. The recovery of fluorine as HF and COF2 for the C6F-ketone is lower compared to HFC 227ea and HFC 125. There is a clear difference in the recovery of fluorine for Halon 1301 where an almost quantitative recovery as HF or COF2 is found. Halon 1301 additionally contains bromine, which, to a large extent, is recovered as HBr.