The use of light scattering and ion chamber responses for the detection of fires in diesel contaminated atmospheres

Experiments were conducted to determine the optical scattering properties of diesel particulate matter (DPM) and various combustion aerosols from both flaming and smoldering combustion sources at discrete angles of 15degrees and 30degrees in the forward direction and at a light source wavelength of 635 nm using a simple light scattering module. In addition to the scattering data, simultaneous measurements were made of the total aerosol mass concentration; light extinction at an average wavelength of 546 nm; and the response of a common bipolar ion chamber typical of residential smoke detectors modified to allow the aerosols to flow through the chamber. The results of these experiments indicate, for DPM and combustion aerosols, the intensities per unit mass concentration depend not only upon whether the aerosol is DPM or combustion aerosol but also upon the type of combustion aerosol. The results also indicate that the ion chamber responses are greatest for DPM, followed by the response to flaming combustion aerosols (FCA) and lowest for smoldering combustion aerosols (SCA). For light scattering, the greatest intensities are found for SCA, followed by the intensities from FCA, and lowest for DPM. This report describes the experiments, their results, and the use of these results to develop design criteria for early warning fire sensors capable of the rapid and reliable detection of fires in atmospheres that may or may not be contaminated by the products produced from diesel engines. (C) 2002 Elsevier Science Ltd. All rights reserved.