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in mines the escape of methane or other natural gas from layers of minerals and surrounding rock in underground workings. There are different types of gassing: ordinary gassing, fumarole gassing, and sudden gassing. Ordinary gassing takes place slowly but continuously from fissures and pores throughout the entire free surface in coal and rock; it increases when coal is separated from the main body. Fumarole gassing is the local liberation of gas from fissures, a fountain of gas that may be active for a long time. Sudden gassing consists of local, turbulent liberation of large quantities of gas for a short period of time, accompanied by destruction of the face. Gassing is controlled effectively by degasification of the minerals and surrounding rock.