Qualitative analysis, process hazard analysis, thermal evaluation, and fault tree analysis were applied to a flashing accident involving a storage tank that contained acrylonitrile-butadiene-styrene (ABS) powder in Taiwan. The accident was caused by combustible powder attached to the inner wall of the tank reaching a high temperature and then melting. Thereafter, the molten powder became glue-like and dropped onto the ABS powder, burning at the tank bottom, causing decomposition of the styrene and butadiene derivatives as well as other combustible gases. The high concentration of combustible powder and low ignition temperature triggered the powder, initiating a dust explosion. Finally, we analyzed the findings of each method and examined the properties of ABS powder, realizing that the root cause of the accident included an insufficient understanding of the characteristics of ABS and the failure to comply with the management procedures of hot work. Recommendations and countermeasures were proposed that could proactively ameliorate process safety.