Bertsch, Wolfgang. Chemical Analysis of Fire Debris: Was it Arson? Analytical
Chemistry News & Features. September 1, 1996. p 541-545.
Abstract: Forensic chemists work with physical evidence to determine
if there are residual materials in the fire debris which indicate arson.
The results of "normal" fires and those that have been accelerated
by fuel such as gasoline are different. In a normal fire, energy taking
the form of hot gases moves upward, and if fuel is available, the fire spreads
vertically. A room filled with hot gases at the ceiling may create other
sources of ignition. Once the temperature increases sufficiently, these
gases, soot and pyrolysis products can ignite, spreading the fire across
the top of the room and possibly into adjacent spaces. Flashover results
when the layer of hot gases initiates further thermal decomposition of other
fuel sources. Now, temperatures rise rapidly and spread downward, even distributing
the heat. When oxygen content in a confined space drops rapidly, further
pyrolysis takes place.
On the other hand, fires produced via an accelerant produce a large amount
of heat from the readily available fuel vapors within a short time and at
a specific location. In extreme cases, rapidly expanding gases cause windows
or doors to blow out explosively. With liquid accelerants, the available
oxygen may be quickly consumed, leaving excess fuel. While the flames are
intense, the amount of heat and its rate of transfer into the matrix may
not be sufficient to sustain combustion.
With that introduction, the article continues with a detailed explanation
and analysis of different accelerants, their chemical compositions, the
scientific methods of detecting them, and the challenging nature of analysis.
Analysis with gas chromatography and mass spectrometry is discussed and
graphs are presented.