One of the most dangerous hazards occurring in the process of underground mining production is a methane hazard caused by the release of methane gas into mine workings. The flammability and explosiveness of this gas lead to significant, and oftentimes catastrophic, consequences that endanger the ongoing mining operation. To reduce them, it is necessary to conduct research to reliably assess the status of this hazard. Having addressed this issue, the article presents the results of study aimed at developing an effective methodology for assessing the state of methane hazard. This methodology was based on the results of measurements in real conditions and a model developed using fuzzy set theory. The construction of the structure of this model is based on the method of clustering measurement data and fuzzy inference in accordance with the Takagi-Sugeno-Kang model. As a measure of the state of methane hazard, the value of the methane hazard index (MHI) – determined by the fuzzy model – was adopted, taking into account the results of measurements of ventilation parameters by the automatic gasometry system. The paper discusses the developed methodology and model as well as presents the results of the study for a real operating longwall. The comparative analysis carried out showed that both the developed methodology and model make it possible to obtain reliable values of the methane hazard index. The practical application of the findings, especially to support the process of mining production safety management, should improve this safety and the efficiency of the entire mining production process.