Study Of The Effect Factos On The Accelerant Identification In Fire Debris Analysis

With the prosperity of economy and diversification of social development, the occurrence of fire accidents increases gradually, which severely damages the security of person and property. Fire investigation, as a burgeoning intersect discipline, is a research orientation of great difficulty and considerable uncertainty. Due to the complexity of fire process and presence of human factors in the extinguishment, it is difficult to extract and identify the accelerants in the fire residues. Hitherto, the intensive analysis on the influence factors of identification of accelerants is still scarce. Therefore, a series of experiments were performed to investigate the possible effects that pyrolysis, volatilization, etc. cause on the identification of flammable liquids.Firstly, a brief summary on the common extractive techniques and detection and analysis techniques in the identification of accelerant is drawn, the Solid-phase Microextract (SPME) and Gas Chromatography-Mass Spectrometer (GC-MS) technology is chosen as the optimal analysis technological path for the subsequent experiments.The concept and mechanism of pyrolysis in fire debris analysis are introduced in this paper. A series of controllable fire events are conducted to study the pyrolysis products of the polymers commonly seen in fire situations. Pyrolysis mechanism are employed to analyze the products, and the products are also compared with the results under instrument conditions. Some target components readily found in ignitable liquid residues are detected in the pyrolysis products, which may lead to a negative result during the fire debris analysis. Due to the presence of oxygen and the uneven heating during the fire process, the difference of the pyrolysis products between the burn condition and instrument condition is apparent.A series of experiments are conducted to study the effect that the pyrolysis products may have on the recognization of accelerants, while gasoline is chosen as a representative material of ignitable liquids. It is found that the main characteristics of the pyrolysis products in the total ions chromatograms are retained after the addition of gasoline, but it is also been destroyed at some extent, which is reflected in the missing of some kinds of compounds and the content of some compounds is also changed. The content of the target components of gasoline is generally low, thus the characteristic materials of the polymer, obtained from the total ions chromatogram of the sample, are predominated. This may be attributed to the less addition of gasoline, or the volatilization and combustion of gasoline during the experimental process. Different polymer materials impose different distractions on the identification of gasoline.A series of experiments on the volatilization of93#gasoline are conducted, a software is compiled using Pearson Product-moment Correlation Coefficient (PPMC) to rapidly recognize the relevance between each sample, the migration patterns and architectural feature are studied also. In addition, controlled combustion experiments between gasoline volatilized to different degrees and wood are also performed in order to study the influence of volatilization has on the architectural feature of the compounds in fire debris.