Fires of suspicious origins are often investigated by the Vermont State Police arson squad. These investigators will inspect fire scenes in an attempt to determine what caused the fire. In their inspection of the scene, they may take a sampling of the fire debris for the laboratory to examine. If a combustible liquid (known as an accelerant) such as gasoline or diesel fuel was used to start a fire, a residue of this material may still be present after the fire. The laboratory's role is to try to determine if a particular accelerant is contained in the submitted debris. This laboratory uses a carbon absorption method to collect the accelerant followed by gas chromatography/mass spectrometry to analyze the collected material.
New metal paint type cans are used to collect fire debris. The forensic scientist inserts a carbon strip into these cans and warms the can and debris. Any volatile material is driven from the debris and is absorbed onto the carbon strip. The carbon strip is removed from the can and washed with a solvent to release the trapped material. Gasoline, diesel fuel, or other accelerants contained within the debris are now contained within the solvent, which can be injected into an instrument known as gas chromatograph/ mass spectrometer (GC/MS). Most commonly encountered accelerants are composed of a certain combination of substances. The GC/MS instrument is used to separate mixtures into individual substances and then attempts to provide a chemical identification for each substance (see drug analysis section for additional details). Once a sample is analyzed using the above method, the forensic scientist reviews the instrumental data to determine what accelerant, if any, the debris contained. This method is extremely sensitive as it can detect about 1/1000th of a drop of an accelerant.