Propylene oxide (PO) is commonly employed as an intermediate for polymerization. Due to its unstable structure and extensive heat release during disturbance, PO has caused many thermal explosions during the manufacturing process. This study employed a C80 calorimeter to investigate the properties of PO when combined with various materials. The kinetic and safety parameters were evaluated via numerical simulation, and the runaway scenarios for a barrel of PO containing different contaminants were subsequently calculated. The results indicated that refined PO is thermally stable, even at high temperatures, but contaminants, such as water, acid, base, and metal ions, could accelerate the reaction dramatically. (c) 2014 American Institute of Chemical Engineers Process Saf Prog 33: 369-373, 2014