ABSTRACT
Every time large quantities of gaseous combustibles are released, there is high chance of having an unconfined vapor cloud explosion (UVCE). There are no well-defined theories to foresee if the explosion of a combustible unconfined mixture will be a deflagration or if it will be a detonation whose effects are much more serious. The development of an explosion is conditioned from the reaction piloting the shock wave. UVCEs show a quite different behavior from an ideal explosion, essentially because when a cloud explodes small energies per volume unit are released in relatively important times. Even if the overpressure wave form in a UVCE is typical of each explosion, usually trinitrotoluene blast wave is taken as reference. Conditions created from explosions and/or from fires associated with explosions can be worsened by the presence of particular materials dangerous to the health. Physical protection against sabotage and against diversion of dangerous substances is a problem of growing importance.
