Department of Safety, Health, and Environmental Engineering, National Yunlin University of Science and Technology (NYUST) NO.123, University Rd., Sec. 3, Douliou, Yunlin, Taiwan 64002, ROC Abstract For ensuring the fire/explosion safety associated with flammable chemicals in process industrials nowadays, the explosion limits and safety-related information of loading materials are imperative to know beforehand for fire accident prevention and protection. In terms of 20-L-Apparatus, this study attempted to investigate the flammability characteristics of methanol with different inerting gases (i.e., carbon dioxide (CO2), helium (He), argon (Ar), and nitrogen (N2). The target flammability characteristics parameters, including explosion limits (LEL and UEL), minimum oxygen concentration (MOC), maximum explosion pressure (P(subscript max)), maximum rate of explosion pressure rise (dP/dt)(subscript max), and gas or vapor deflagration index (K(subscript g)) were detected under initial testing conditions of 760 mmHg, 150/200 ℃ and various loading oxygen concentrations. In addition, the specific inert effects of above inerting gases were also demonstrated in our flammability experiments. According to testing results, it was concluded that the inerting influence on methanol by CO2 was better than He, Ar, and N2. The outcomes of this research could be very useful for the relevant process safety control systems to avoid fire and explosion accidents, and to promote the process safety progress on the whole.