Comparative analysis of methods for studying soot sediments at fire places
Authors:   Ural Institute of State Fire Service of EMERCOM of Russia, Medvedev A. Yu. , Belshina Yu. N. ,   Saint-Petersburg University of State Fire Service of EMERCOM of Russia
Published: December 2021

Introduction. Smokes are aerosols that contain sublimating substances and condensing vapors, as well as products of chemical and photochemical reactions. In addition to solid and liquid particles, they contain gaseous products of both complete and incomplete decomposition during combustion process, as well as nitrogen and the remains of unreacted oxygen during combustion. The aerosol substance of smoke that has settled on any surface is called soot, which often acts as an object of fire-technical expertise, and the aggregate of soot particles that form zones of various configurations is called smokiness. Goals and objectives. The aim of the work is to study soot and its components for the development of a comprehensive methodology for the study of fires in determining both the focus and the cause of the fire, as well as the pathways of the spread of hazardous factors of fire at different stages of fire development. The main task of the work is to determine the dependence of the qualitative and quantitative indicators of soot and its component composition on the temperature conditions of combustion of various materials in order to establish the conditions for the course of a fire. Research methods. Field and laboratory methods for the study of soot are considered. Field methods include visual analysis of soot deposits (identifying the configuration of soot, color and intensity of the soot layer) and measuring the electrical resistance of the soot layer using a field contact probe. Laboratory methods include the method of microscopic morphological analysis, the method of thermal analysis, molecular spectroscopy and gas chromatography, which are indirect and direct methods for studying extracted organic components of soot. Results and its discussion. The modern methods of research of soot are analyzed. A scheme of laboratory methods is proposed. It allows carry out full morphological analysis, to evaluate the behavior of soot components during heating and composition of extracted components for solving the problems of studying fires. Regression dependences of the content of bituminous components on the logarithm of the electrical resistance of the soot layer were obtained, which showed that, regardless of the type of combustible material, a transition zone is observed on them, in which, with a relatively small change in electrical resistance, a significant increase in the content of bituminous components is observed. Conclusion. The paper considers an comprehensive approach to the study of extractable components of soot. The obtained dependences of the qualitative and quantitative indicators of soot and its component composition on the temperature conditions of combustion of various materials will improve the quality and level of reliability of information in the study of fires in order to determine the focus and cause of a fire, as well as the ways of spreading hazardous factors of a fire at different stages of its development. Key words: smoke, soot, extractable organic compounds, bitumen components, soot layer electrical resistance, molecular spectroscopy, Boltzmann function, fire investigation.