Such planning requires a vulnerability assessment of the building, an estimate of the risk of attack, an evaluation of the current physical security measures, delineation of the lines of authority, and periodic review and updating of the security scheme for such incidents. Planning for the evaluation of a bomb threat must address the timely communication of a threat, who evaluates threats, and a chain of authority. The issue of who performs the searches must be determined. The search should include inhouse personnel since they are familiar with the building and the placement of various equipment and materials. Factors in the evaluation process include determining how much the loss of production will cost, how to ensure that everyone evacuates, how to control evacuees, where to place the evacuees, how long to make the evacuation, the distance between the building and the evacuation location, and the effects of the threat and evacuation on customers. Damage control in the event a suspected explosive device is found includes the shutdown of utilities such as natural gas lines, venting, barricading, and the use of bomb blankets.