Low Velocity Explosions

A low velocity methane explosion will originate when the initial ignition has no confinement and the flame front propagates into the explosive mixture of methane with no pressure wave. This is how the old fireman would burn the gas off prior to the commencement of production. Ignite the gas from an unconfined location (open end of a roadway). The flame front propagates at a relatively low velocity compared to a confined ignition. The velocity pressure of the explosion is in the opposite direction to the explosion and the flame duration is much longer. This is still an explosion, not a fire. The consequence of the explosion is a much longer flame duration resulting in much more serious burns and flame damage. This explosion is much more likely to start a fire rather than a coal dust explosion. There is no preceding pressure wave in a low velocity explosion. Notice the paper sealing the chamber in one demonstration. It is not displaced by the explosion.