Marley, Ronald K. The Facts about Coiled Metal Springs in Fire Investigations. Fire Engineering. Vol. 149. No. 8 (August 1996). p 105-108.

Abstract: Investigators know that springs do collapse during fire. But, the presence of collapsed furniture springs has been improperly analyzed to indicate cause and origin. In fact, there is little evidence that can be gained from springs alone that is indicative of a fire's cause. The comparative information required regarding a spring in its pre-fire state is often unavailable or unreliable.

Research into mattress springs reveals up to 11% differences in height, depending on the spring's location in the mattress. And spring height varies according to the condition of the furniture. Investigators using collapsed springs as an indicator of an accelerant in that location would be hard-pressed to verify the springís pre-fire condition.

The amount of carbon in a spring will also effect its collapse, the lower the carbon content, the faster collapse will occur. To analyze a spring on this basis, again, its pre-fire carbon content would need to be determined. Analysis of a spring's post-fire hardness is not accurate either, because hardness is affected by cooling rate, and it is possible for a springís post-fire hardness to be the same, higher or lower than before the fire. Another factor to be considered is any load imposed on the spring from falling debris during the fire that would change its compression, but would not reflect the spring's relationship to the fire.

When analyzed along with other evidence, collapsed springs may provide useful information regarding a fireís origin. They cannot, however, be used to pinpoint cause or origin.

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