The most common gases found within a coal seam is methane. Methane is a gas that is highly flammable within it’s explosibility limits (5% – 14%). Methane is released from the coal seam as coal is being extracted and is vented into the mine atmosphere. The amount of methane within the mine air has to be monitored and is usually measured by methanometers. Methanometers are located at fixed positions around the mine, such as the longwall face and development machinery. They can also be used as hand held monitors by shift supervisors. The levels of gas that are permitted in the mine atmosphere can be found in the CMRA 1984. Other mine environment gases that are to be monitored are Carbon Dioxide (CO2) and Hydrogen Sulphide (H2S).
In order to control the amount of gas being released into the mine atmosphere while extracting coal some mines incoporate a gas drainage program. This reduces the amount of gas being released into the mine atmosphere during mining. Gas drainage simply involves drilling holes into a new longwall panel and then allowing the gas to drained out where it is piped to the surface. Some mines use the methane gas to generate electricity via a gas turbine power station.
For additional information, refer to the University of Wollongong Outburst Websiteby