Blast events are defined by two distinct phases - an initial “positive” phase where the full amount of the explosive pressure specified is loaded onto the assembly and a secondary “negative” phase where the pressure dissipates below the ambient pressure creating force in the opposite direction which is known as “rebound”. The additional contributing factor to the rebound force is through the “spring” effect of the door panel. The peak positive pressure load will cause the door panel to deflect. When deflection occurs but does not pass the yield point where deflection is permanent, the door will spring back during the rapid dissipation of pressure from peak pressure through to the negative phase. This “bounce back” also contributes to rebound force. The extent of the pressure during the rebound phase can be expressed as a percentage of the initial blast pressure. This figure ranges from zero percent to one hundred percent. This also is commonly expressed as true rebound, where the rebound affect is determined based on the door construction and stiffness.