Structural behaviour during an explosion depends on the materials used in the construction of the building. Upon hitting the face of a building, the shock front from an explosion is reflected. This impact with the structure imparts momentum to exterior components of the building. The associated kinetic energy of the moving components must be absorbed or dissipated in order for them to survive. Generally, this is achieved by converting the kinetic energy of the moving component to strain energy in resisting elements. Typically the resisting elements—such as windows, building facades and support columns—fail, causing partial damage through to progressive collapse of the building.