In the chemical industries the three most common accidents are due to toxic releases, fires, and explosions, with most occurring in the form of fires and explosions. The reasons for these accidents predominantly arise out of a lack of awareness of flammability properties of flammable substances. To evaluate the fire/explosion hazards involved and ensure the safety and optimal operation of reactors, vessels or storage tanks, it is necessary to recognize the flammability characteristics of flammable materials. By means of a 20-L-Apparatus, we investigated the flammability and explosion characteristics of methane with three different inert gases (CO(2), N(2), and Ar) at 1 atm. 30 and 100 degrees C, and many air concentrations. Our test results determined that the inert influence on methane by CO(2) is better than N(2) and Ar. The results of this article include graphs that show the lower and upper flammability regions and the explosion characteristics for these inerted systems. The flammability ranges include results for 30 and 100 degrees C. (C) 2010 American Institute of Chemical Engineers Process Saf Prog 29: 349-352, 2010