Vapour cloud explosion and flash fire

When a leakage occurs on an equipment item, a gaseous release can occur, either directly, or following the gradual vaporization of a pool on the ground close to the leakage. This event leads to the formation of a cloud that drifts and disperses with the wind. If the substance is flammable, there is an intermediate zone in which the vapour concentrations in the air are between the flammability limits of the substance. A sufficiently energetic ignition source, on the trajectory of the flammable zone of the cloud, may ignite this cloud. According to the front flame speed, the accident will lead to a flash fire or a VCE (vapour cloud explosion). The latter event causes an overpressure – underpressure wave. A devastating effect is associated with the peak overpressure as well as with the wave shape.