In a wide-ranging analysis of the effects of weathering and biological degradation on ignitable liquids, researchers at the University of Central Florida’s National Center for Forensic Science studied 50 liquids in the Ignitable Liquids Reference Collection (ILRC) database. The study, supported by the National Institute of Justice, was the most comprehensive analysis of the effects of weathering and biological degradation yet done, the researchers said. The results were included in the ILRC database, and a “best practices” statement was developed to “inform forensic practice and policy in laboratories conducting fire debris analysis.”In the aftermath of a fire, investigators often face the daunting task in trying to determine if ignitable liquids such as gasoline or other solvents were involved in starting the blaze. Discovering and identifying flammable liquids after a fire is more difficult due to the effects of weathering, primarily through evaporation of volatile compounds, and biological degradation, which can alter the chemical signature of the liquids.
The ignitable liquids studied, representing the many “designated classes” of the American Society for Testing and Materials (ASTM) International, ranged from gasoline to oxygenated liquids. Each liquid was “weathered” by removing various amounts of the original volume to simulate evaporation. Biological degradation was accomplished by placing small amounts of the liquids in potting soil and allowing them to degrade for time periods running up to 21 days.
Researchers said that the underlying concern was the possibility that weathering and biological degradation “would lead to failure to identify the presence of an ignitable liquid reside.” Not only could these factors mislead analysts, they could “decrease the ability of automated techniques to properly assign liquids into ASTM classes” the researchers said.
Since the study concluded, the results on how to better identify weathered and biologically degraded liquids have been made available on the ILRC database web site and have “had an impact on fire debris analysis practices and policy within individual laboratories.”
About This Article
The research described in this article was funded by NIJ cooperative agreement number 2011-DN-BX-K539, awarded to the University of Central Florida. This article is based on the grantee report “Degraded Ignitable Liquids Database: An Applied Study of Weathering and Bacterial Degradation on the Chromatographic Patterns of ASTM E 1618 Ignitable Liquid Classes” (pdf, 105 pages), by Michael Sigman and Mary Williams, University of Central Florida.