Volatiles from carpet: A source of frequent misinterpretation in arson analysis

Abstract

Carpet and carpet padding are frequently submitted to laboratories for the analysis of residual accelerant in suspect arson cases. Charring and pyrolysis of the above matrixes produces volatiles that can cause interferences with some accelerants, most notably gasoline. A study was conducted to evaluate the interference potential of pyrolysis products obtained from simulated fire debris samples and from samples collected in the field. It was found that variable amounts of alkylbenzenes and naphthalenes are produced, along with large quantities of styrene and alkylstyrenes. Small amounts of higher-molecular-mass aromatic hydrocarbons are also generated but no alkanes or alkenes appeared. Since aromatic hydrocarbons are the major diagnostic components in gasoline, a potential interference is indicated. Careful observation of patterns within each group of isomers is required to rule out interferences. The distribution of alkylbenzenes in gasoline is quite different from the patterns produced by pyrolysis. Guidelines are proposed to distinguish between petroleum-based aromatic hydrocarbons and those derived from the pyrolysis of carpet/carpet padding. Mass fragmentography was found to be particularly useful toward the discrimination of interferences.