Many devices used in the chemical or petrochemical industry involve hazards because of the existence of flammable gases. Thus, the lean and rich flammability limits are very important characteristics of homogeneous gas mixtures. These data are documented and summarized in various reports, but there are discrepancies between the reported limits. Also, there is a lack of data for mixtures of flammable gases. To complement experimental measurements, the calculation of the flammability limits is of tremendous interest. This article reports a computational study of premixed CH3OH/air and CH3OH/CH4/air flames close to the flammability limits using detailed chemical models and transport properties and comparing the results with data from experiments. A comparison between the results and flammability limits calculated by the Le Chatelier principle is also performed. The deviations are stated, and the causes are explained on the basis of detailed reaction flow analyses.