From the Fire Into the Frying Pan
Fire science metallurgy proves turning point of case
On a hot July night in rural Mt. Airy, Md., three adults and one child were asleep on the upper floor of their early 1900s farm home. Shortly after midnight, a thunderous rumble followed by a loud crack awakened them all. They rushed from their rooms to find the smoke alarm blaring and a fire downstairs. Everyone made it safely outside except one man who mistakenly thought his wife was trapped indoors and bolted back in the house to find her.
Fourteen months later, conjecturing the fire was caused by a malfunction of a propane-fueled stove, the family’s attorney filed a $650 million lawsuit against a propane company and its parent company, later naming additional third-party defendants. A forensic engineering company needed to be brought in on behalf of the defense to determine the fire’s cause. Fire science metallurgy indeed provided the clues to help find the probable truth about what happened that tragic summer night.
Little to Go On
When the forensic engineering company came on the scene, the site had already been bulldozed and grass was growing again. Four propane tanks from the site had inadvertently been disposed of months earlier. It seemed the odds were against the company being able to assist in the case – until investigators located the home’s stove just to the left of a shed on the property. It was badly damaged and rusted. Inside was the stove’s oven rack and, just below it, a cast-iron skillet, which was deformed but hadn’t melted.
Melting and Oxidation Yield Clues
Study of this skillet’s melting temperature and patterns and oxidation disproved the propane-fire theory. For one thing, with melting temperatures between 2,100 degrees F and 2,600 degrees F, the cast-iron skillet’s condition indicated that such temperatures were not achieved during the fire – a sign the fire temperatures were not intense in the oven, as was claimed by plaintiffs. A full exposure to the fire would also have destroyed the chrome-plated carbon-steel oven rack, which survived. Examining the oxide formation on the skillet, the engineering firm concluded that the fire in question burned no hotter than 1,800 degrees F. Although the rest of the cast-iron skillet survived largely intact, its handle had begun to melt. Such localized melting suggests that the stove’s ambient temperature was not at cast iron’s melting point; this melt pattern would have occurred when the oven door partially opened during the fire, causing a “blowtorch” effect directing intense heat on portions of the handle.
Fortunately, there was just enough evidence left to allow the engineers to uncover what really happened in this case. The conclusion – with which the jury concurred – was that the fire was most probably electrical in origin, initiated by an electrical fault.
All parties involved in accidents or natural disasters are encouraged to support the preservation of all evidence at the scene. As Crane Engineering’s Maryland case shows, it may make all the difference in investigators’ ability to arrive at concrete conclusions.
- John E. Brynildson, P.E., Metallurgical Engineer