To smoothly deliver crude oil, the crude oil piping system adopted by petrochemical plants must be maintained at a high temperature. This study investigated a fire accident by collecting fire debris and related combustibles as experimental samples and employed calorimetric approaches in fire testing the spontaneous combustion of crude oil sludge. Moreover, thermal analysis experiments were conducted. The results demonstrated that although the clean insulation material was flame resistant, after absorbing a large amount of crude oil sludge, the material underwent an exothermic reaction of enthalpy 247.39 J/g with a weight loss of 33.98% when its temperature reached approximately 170 degrees C. The heated temperature of the bulk bags widely used in the industry is approximately 204 degrees C, which has an exothermic reaction of enthalpy 98.60 J/g; at approximately 399 degrees C, an exothermic reaction of enthalpy 117.74 J/g resulting in a weight loss greater than 96.23% occurs. The results from each experiment conducted in this study are expected to serve as a reference for preventive measures against thermal hazard accidents involving insulation materials.