Analysis of the Light Extinction Effect of Polymethyl Methacrylate by Smoke Particle Size in Combustion Conditions

Abstract

Large amounts of smoke and toxic gases generated during combustion are the main causes of fire casualties and are major factors that hinder evacuation (i.e., by reducing the visibility). Since the size of the smoke particles closely influences the scattering and absorption of light, it has a direct effect on the opacity of the smoke. Therefore, it is important to determine the correlation between the particle size distribution of smoke particles and smoke opacity to ensure the safety of evacuees. In this study, the correlation between density and size distribution of smoke particles from polymethyl methacrylate (PMMA) and visibility were measured with and without flame conditions. We achieved this by setting up an ISO 5659-2 smoke density chamber, equipped with a particle measuring device (OPC), and recording the visibility changes with increasing temperature. Specific optical density and visibility secured during evacuation were compared. As the specific optical density increased, the particle concentration with a size of 0.25 - 0.3 μm decreased but the one with a size of 0.3 - 0.58 μm increased significantly. Regression analysis confirmed that 0.25 - 0.58 μm particles affected light extinction the most. The difference in visibility secured during evacuation was determined based on the number of particles and size distribution.