Residual Characteristics of Ignitable Liquid Components under Various Post-Fire Conditions

The interpretation of ignitable liquid residues (ILRs) is a key scientific procedure in determining the cause of fires and identifying potential arson cases. However, variables such as the extent of burning, the use of fire suppression agents, substrate characteristics, sampling delays, and thermal exposure complicate the analysis. In this study, gasoline and diesel were applied to two representative substrates—carpet and an interfloor sound insulation mat—and subsequently exposed to controlled burning, suppression, and post-fire conditions. Gas chromatography–mass spectrometry and extracted ion chromatogram analyses were performed to evaluate whether residual components were identifiable under varying post-fire processing conditions. The results showed that although the use of suppression agents reduced the overall residue detectability, the retention and visibility of the ILR were more strongly influenced by the substrate characteristics and fuel type. Delayed sampling and thermal exposure accelerated the loss of low-boiling-point components, and most ignitable liquid residues were volatilized after exposure to 250 °C. This study provides practical insights into priority considerations for sampling and storage procedures at fire scenes and offers analytical interpretation guidelines that can enhance the reliability of fire debris examination and ILR pattern analysis.