Optical Measurement of Toxic Gases Produced during Firefighting Using Halons

Abstract

Several optical techniques (FT-IR emission and absorption spectroscopy, mid- and near-infrared tunable diode laser absorption spectroscopy) have been used to measure toxic gases produced during inhibition of flames by halogenated hydrocarbons (Halons). Fire types studied include low-pressure premixed flames, counterflow diffusion atmospheric-pressure flames, open-air JP-8 (turbine fuel) fires, and confined JP-8 fires. Spectra are presented and analyzed for these fires inhibited by CF₃Br (Halon 1301) and C₃F₇H (FM-200). For low-pressure premixed flames, spectra are presented which show production of the CF₃ radical in methane/oxygen/Ar flames inhibited by CF₃Br. For large-scale fire testing, it is shown that the type and amount of toxic gases produced during fire inhibition are highly dependent on fire conditions and temperatures and that some species not considered important (CF₂O) are often produced in significant amounts. Finally, it is shown that HF production, during inhibition of vehicle fires using FM-200, is highly dependent on time to suppression.