Mine explosions have long been known as a catastrophic risk in underground coal mining. Since 1970, the U.S. coal mine industry experienced 12 major disasters associated with methane explosions; most of which occurred during a significant drop in barometric pressure. Several of these disasters and numerous other explosions of lesser consequence suggest involvement of explosive gas zones (EGZs) or explosive methane-air mixture. Previous studies by researchers at the Colorado School of Mines (CSM) have been aimed at locating and reducing EGZs in longwall gobs but little work has been done to investigate the effect of barometric pressure on these EGZs. In a new research project at CSM, funded by The National Institute for Occupational Safety and Health (NIOSH), the authors investigate how the locations and volumes of EGZs in bleeder ventilated longwall gobs change with decreasing barometric pressures. This work is being done using Computational Fluid Dynamics (CFD) modeling. In the simulated longwall panel, the authors found that the decreasing barometric pressure significantly affects EGZs size and shape. During barometer drops, explosive methane may expand and migrate from the gob into active working areas, exposing miners to potential hazards of explosion and fire. Research results suggest the need for thorough gas monitoring along the periphery of the longwall and in the bleeder entries.