The sudden release of energy of sufficient magnitude to create a pressure wave. The energy to produce an explosion may come from a variety of sources; including nuclear, pressure or chemical reaction. 1. Examples of pressure related explosions include a rapid change in state (liquid to gas, for example) or by the over pressurization of a container (i.e., the failure of a gas cylinder). 2. A chemical explosion is the event in which a quantity of matter is instantaneously converted to gaseous product, with the generation of high temperature and pressure.