Three-wavelength light transmission technique to measure smoke particle size and concentration

This paper describes an optical technique and instrumentation for measuring the average particle size and mass concentration of smoke. Transmission through the smoke at three wavelengths (0.45 microm, 0.63 microm, and 1.00 microm) is measured using a white light source and a compact, three-wavelength detector assembly. Sizes and concentrations are then calculated from the transmission data using Mie theory. Graphs of the calculated Mie extinction coefficients are presented for several complex refractive indices. This three-wavelength optical technique was used to study smoke from a wood-tunnel fire, and the results are compared to those of other sizing techniques.