Mining coal is much like working in a natural gas well.
The same things that produce coal and oil — dead organic material, heat and pressure — also produce natural gas, whose primary constituent is methane. The gas is trapped in a coal seam or petroleum reservoir by pressure and water, only to be released when workers drill into the strata.
“It’s a tremendous nuisance,” said mining engineer Christopher J. Bise of West Virginia University. “It’s colorless, odorless and tasteless, but highly flammable.”
The gas is explosive at concentrations of 5% to 15% in the air, with the most violent explosions occurring at concentrations of about 9%.
The traditional way of dealing with the gas is “to overwhelm it with fresh air,” Bise said. Massive exhaust fans at some mine entrances suck air out of the shafts, pulling fresh air in through other entrances and circulating it through active mining areas.
Although many experts believe that methane was responsible for the West Virginia explosion, it is not the only threat in such mines, according to mining engineer David Summers at the Missouri University of Science and Technology in Rolla. Finely powdered coal dust — and many other fine powders — can also be highly explosive, as witnessed by the occasional explosions of grain elevators produced by dust from the grain. It is more explosive than methane, Summers said.
Full story: Coal mines’ gas problem – latimes.com