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FEBRUARY 1990
ARSON INVESTIGATIONS
By
William A. Tobin
Special Agent
FBI Laboratory
Washington, DC
Collapsed furniture springs, which have been subjected to
fire, have been used by arson investigators for many years, both
as an indicator of arson and/or of a slow, smoldering source,
such as a cigarette. However, FBI Laboratory research has
revealed that collapsed springs are not a valid indicator of the
presence of an accelerant or of a smoldering source.
A review of the literature reveals that there are
contradictory conclusions regarding the condition of springs
subjected to fire. Some sources maintain that collapsed springs
are, indeed, an indication of a slow, smoldering origin because
of the consistent heat required to collapse them. Others argue
that collapsed springs are positive proof of the presence of an
accelerant because the temperature required to collapse the
springs cannot be reached by the burning of normal building
materials alone. The contradictory nature of these conclusions,
therefore, suggests that a detailed metallurgical investigation
was necessary to determine which theory was valid.
When metals are subjected to elevated temperatures, many
metallurgical parameters and considerations can come into play.
Metallurgists have long known, for example, that in order for a
metal to be of equal strength, it must be heated to a certain
temperature in a certain amount of time. This can be
accomplished by applying twice the heat in half the time, or half
the heat in twice the time. The FBI Laboratory's investigation
examined not only the interactions of time and temperature but
also of chemical composition, fabrication history, and other
metallurgical conditions.
Part of the FBI's investigation involved actual test
burnings of mattresses of varying inner-spring construction. The
mattresses were placed in a room full of furniture at the FBI's
Test Burn Facility in Quantico, VA. To simulate an
accelerant-based fire, gasoline was poured on the mattresses and
ignited. To simulate a cigarette or other slow, smoldering type
of fire, 10 ml of propanol was placed on the mattresses and
ignited. After the resulting fires were allowed to burn for
varying amounts of time, they were extinguished and data,
including photographs, were collected. The most notable
conclusion was that within the same mattress, there were both
collapsed and uncollapsed springs. Therefore, consistent with
metallurgical expectations, controlled testing revealed that the
collapsed, partially collapsed or uncollapsed condition of
furniture springs is of no value as an indicator of arson or of a
slow, smoldering fire.