Application of Dynamic Headspace Analysis to Laboratory and Field Arson Investigations

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Abstract
A dynamic headspace procedure has been adopted to meet the special needs of the forensic scientist engaged in detecting and identifying trace accelerants present in physical evidence recovered from fire scenes. For common accelerants, sorbent trap concentration followed by thermal desorption directly onto a gas chromatographic column enhanced sensitivity by two orders in a magnitude over a static headspace technique. The procedure reduced negative findings 38% and inconclusive determinations 60% relative to static headspace analysis. Air at fire scenes can be drawn through a trap with a portable pump to allow monitoring for trace amounts of organic substances. The trap is then forwarded to the laboratory for analysis. Special precautions in sampling methods, transportation, and storage will be discussed as they relate to assuring the integrity of the collection and analysis of a fire scene atmosphere.