Since 1958 there have been 16 major coal mine explosions in the U.S. claiming 323 lives._x000D_
Whilst the exact cause of a number of these incidents has not been determined, the majority has involved gas ignitions in one way or another._x000D_
In addition there have been fatal gas explosions in salt mines and vapor explosions in oil mines._x000D_
Furthermore, many of the oil shale mines in the U.S. have proven to be gassy giving cause for concern. Compounding these problems is the fact that frictional ignition of methane in coal mines has dramatically increased over the past several years; over 100 such ignitions were reported in 1979. While, no fatalities have been attributed to frictional ignition in the U.S. since early 1978, a recent mine explosion in Nova Scotia which resulted in 11 fatalities was attributed to a frictional face ignition. Research being conducted at the Bureau of Mines is aimed at the prevention and suppression of gas explosions. Emphasis is placed on new coal cutter bits for reducing ignition frequency, machine-mounted water sprays for preventing frictional face ignitions and automatic devices for quenching incipient ignitions and fully developed gas explosions.