Abstract: For the cause analysis of difficult fires and the in-depth investigation of accident causes, investigators and technical appraisers need to find out the direct and indirect evidence that can prove the fire. In this paper, by means of video analysis, isothermal microcalorimetry experiment, volatile content determination, gas chromatography-mass spectrometry and other technical means, through multi-level and multi- angle comparative analysis and research on thermoplastic elastomer (SBS) in a warehouse fire, the fire causing substances are given, the specific causes of heat release of SBS are analyzed, and the factors affecting the stability of SBS are given, the cause and mechanism of spontaneous combustion were explored. The analysis and research results show that the SBS involved not only releases heat at low temperature, but also continuously releases heat. The material itself has good heat storage conditions and fully meets the conditions for spontaneous combustion. It is comprehensively analyzed that the fire is caused by spontaneous combustion of SBS.

Key words: SBS, fire video analysis, spontaneous combustion, isothermal microcalorimetry, exothermic reaction, antioxidant, quantitative analysis by GC-MS