Fourier Transform Infrared Analysis of Combustion Gases

The Federal Aviation Administration (FAA) has developed a unique extractive Fourier Transform Infrared (FTIR) system to analyze rapidly changing moist fire gas concentrations as a function of time. The system was designed to eliminate numerous errors generated by state-of-the-art FTIR systems for fire gas analysis. In addition, the path length, cell volume, sample flow rate, and system temperature were optimized to provide a rapid response and a sufficient dynamic range to detect gas concentrations generated in a fire (modified cone) calorimeter. A nonlinear classical least squares method was developed to analyze the FTIR data and generate the concentration histories and confidence limits of the 16 fire gases. Results of the technique are presented for flaming and nonflaming combustion tests of a mix of six common plastics.