An explosion is defined as a very rapid release of high-pressure gas into the environment. The energy from this very rapid release of the high-pressure gas is dissipated in the form of a shock wave.
Explosions can be classified as physical, a balloon bursting, as physical and/or chemical, a boiler explosion, or a chemical reaction of a gas/particle mixture. Our discussion will focus on chemical reaction explosions.
The process of a chemical reaction explosion is similar to the combustion process whereby a fuel and oxidant have premixed prior to ignition such as petroleum vapor or fine particles of grain dust mixed with air.
However, in an explosion the oxidation process proceeds at a greatly accelerated rate. The oxidation process is usually, but not always, confined within an enclosure such as a tank, grain silo, so that a rapid high-pressure rise occurs with an associated flame front. Generally, it is this high-pressure shock wave that causes the damaging effects from an explosion