During the winter months, most mines become dry as a result of cold dry air entering the underground mine where it is warmed and picks up moisture.

The result is drier surfaces and drier coal dust, which can contribute to dust explosion hazards.

“Safety principles should be followed year-round, but miners and mine operators must be more vigilant to safety precautions during wintertime when the weather increases the risk of fatal accidents," assistant secretary for mine safety and health Richard Stickler said.

“As the temperature drops, miners must be aware of how cold weather affects working environments."

MSHA's winter alert campaign runs annually from October through March, and this year's theme of "Don't Let Safety Slip" reminds mine operators and miners to be alert for environmental hazards such as slippery walkways and icy mine access roads, and to make sure safety rules are not compromised because of seasonal changes.

Low barometric pressure, low humidity and seasonal drying of areas in coal mines can cause methane to migrate more easily into the mine atmosphere and coal dust to become dry during colder weather increasing the risk of an explosion.

Other hazards include limited visibility, icy haul roads, and unstable highwalls due to the freezing and thawing process.