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