Visual and oxide analysis of an oil-filled heater fire scene

Abstract

This study demonstrates the use of visual and oxide analyses to identify the cause of an actual electrical fire. Three severely oxidised electric oil-filled heaters and heating elements located at different locations were discovered in the debris of a megamall fire. According to visual analysis, the steel fins exhibited signs of overheating and the presence of large amounts of iron oxidation, denoting that the fins were the probable ignition source. Metallographic analysis showed that oxidation inside the oil-filled heaters at the fire site was also severe. Moreover, the temperature-dependent wear of the metal parts provided new evidence about the exposure temperature of the fire. The microstructure of the oxide scale of metallic materials was also temperature dependent, indicating that metallurgical characterisation will greatly complement conventional evidence collection by way of macroscopic visual examination.