Characterization of smoke from smoldering combustion for the evaluation of light scattering type smoke detector response

Experiments were performed to characterize smoke produced from smoldering materials using light scattering theory. A prototype Scattered Light Detection Instrument (SLDI) was developed to measure the intensity of light scattered at various angles by smoke particles. A Gallium Arsenide solid-state laser was used as the source, with photodiodes used as scattered light receivers. A smoke chamber (8.2 m³) was constructed in which to perform experiments using various fuels. Four different fuels - rubber, cotton, douglas fir (wood), and computer printer paper - were burned in the smoldering mode at various positions with respect to the SLDI within the smoke chamber. Experimental data obtained using a test aerosol of known optical properties indicated general agreement with results calculated using Mie scattering theory. Light scattered by smoke particles indicates that the intensity of scattered light at a given angle changes as the fuel changes, consistent with Mie scattering theory. This suggests that an evaluation method based on detector design parameters and smoke characteristics other than (and in addition to) optical density is possible. The results also indicate that light scattered from smoke produced by different fuels may have varying characteristics which may be quantifiable using particle size distribution, particle number density, and index of refraction.