Ignitable liquids are commonly used during arson attacks and therefore the detection of them is highly important in forensic science to help determine whether the fire had been deliberately started or not and also in determining the chain of events and inclusion /exclusion of suspects. Gas chromatography mass spectrometry is the most commonly used analytical method for detection of ignitable liquid residues, and when coupled with an extraction technique such as activated charcoal headspace it is possible to positively identify the components in the sample and whether they are that of petrol’s composition or not. Despite the importance in the detection of ignitable liquids at a crime scene, many previous studies have focused on using SPME as an extraction technique. This study aims to expand on previous studies by using gas chromatography mass spectrometry, however it also aims to investigate the persistence levels of petrol using activated charcoal probes as the extraction technique. Four building materials were used for this study: carpet, brick, concrete and wood flooring. Each material was impregnated with 2mL of petrol and burned for one minute before being extinguished by smothering. Each of the materials were then packaged and sealed into nylon bags after a period of exposure inside the fume cupboard; this being between zero to eight hours to allow for evaporation to occur. Qualitative results showed that petrol is identifiable on all materials for up to 8 hours. The quantitative findings indicate that petrol persists on wood flooring for longest period of time, as it was less evaporated than the other materials after eight hours. The findings also show that the evaporation of petrol did not surpass 50% on any of the samples, upon comparison to the standard samples which were evaporated in controlled conditions. The outliers in the results highlight the importance of cross-contamination prevention in fire debris analysis and how easily airborne contamination can occur between samples, even when packaged correctly in nylon bags. Further studies into cross-contamination between nylon bags during storage could be carried out to determine if specific conditions, such as temperature, could prevent this. Also extended research could be carried out to determine the length of time that petrol persists after the 8 hours of exposure limit used in this study.
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