Spontaneous combustion is a serious safety hazard in underground coal mines, particularly in mined-out areas (e.g., gob). It is estimated to be the cause of more than 20% of coal mine fires. Pressure balancing is a ventilation technique that can be used to reduce or eliminate the ingress of oxygen to the mine gob (in-gassing), thus reducing the risk of spontaneous combustion. At the same time, pressure balancing can also be used to reduce the risk of methane seeping into the mine ventilation circuits from the gob (out-gassing), due to barometric pressure changes on the surface. Two pressure balancing chambers have been constructed at the West Elk Mine, Colorado, operated by the Mountain Coal Company (MCC): one in a mined-out area, and another close to the active area, near a longwall mine gob. Each chamber is equipped with an isolation stopping, safety doors, a nitrogen injection system, and a set of pressure and environmental monitoring sensors. Several pressure balancing tests for different ventilation conditions have been conducted in these chambers. This study presents a summary of a procedure used to conduct these tests, the results achieved, and the steps taken to reduce the risk of spontaneous combustion.
