.Both benzene and methanol are important raw materials in petrochemical industries worldwide. However, with increased demand in the past few years, the fire and explosion hazards from both benzene and methanol under abnormal conditions have increased rapidly with the demand. This study investigated the flammability characteristics of a binary solution for the mixture of benzene and methanol at various vapor-mixing ratios (100/0, 75/25, 50/50, 25/75, 0/100 vol%) under 150 oC, 760 and 1,520 mmHg by using a 20 Liter Spherical Explosion Vessel. Such work leads to specific safety-related property parameters, including upper explosion limit (UEL), lower explosion limit (LEL), minimum oxygen concentration (MOC), maximum explosion pressure (Pmax), maximum rate of explosion pressure rise (dP/dt)max, and gas or vapor explosion constant (Kg). Along with the results which show that the UEL, Pmax, and Kg all increased with the pressure and oxygen concentration, a triangular flammability diagram was also established. This all serves to elucidate the potential hazards when vapors of different flammable chemicals are mixed.