Coal Mine Disasters: Frequency by Month

Major coal mine disasters (five or more fatalities per accident) in the United States over the past 150 years have tended to occur primarily in the winter months from November through April. Minor accidents (zero to four fatalities per accident) occur at a fairly uniform rate throughout the year. This peak for major disasters is ascribed to effect of barometric minima on the methane content of mine air, to the effect of dry polar air masses in reducing the moisture content of coal dust, and, possibly, to cyclic fatigue of rock structures from cycling barometric pressure. Obvious safety practices are suggested.