A Presidential Emergency Facility (PEF), also called Presidential Emergency Relocation Centers and VIP Evacuation and Support Facilities, is a fortified, working residence intended for use by the president of the United States should normal presidential residences, such as the White House or Camp David, be destroyed or overrun during war or other types of national emergencies. Some Presidential Emergency Facilities are specially designated sections of existing government and military installations, while others are dedicated sites that have been purpose-built. Various sources state there are, or were, between 9 and 75 such facilities.