An explosion is a rapid exothermic reaction within explosive mixtures or an explosive atmosphere, which is characterised by sudden pressure and a sudden bang due to the release of heat which causes a rise in temperature. If the propagation velocity of the reaction is cm/s, deflagration occurs; at a velocity of several km/s a very high-pressure, loud detonation occurs.
An explosion can only occur if certain requirements are met simultaneously. See Fig. 1 Explosion