Prior to the Piper Alpha incident, structural design to limit the consequences of a hydrocarbon explosion was mainly confined to constructing blast walls in the well bay area. These were limited in number and design pressures used were usually low, of the order of 0.1-0.2 Bar. Post Piper, several bars of pressure were found to be a real possibility with realistic levels of congestion and confinement. Little consideration had therefore been given to explosion scenarios on many older fixed structures. As a result of this, little attention was given to design strategies dealing with explosion scenarios.