Any interior building element designed to protect and evacuate the building population in emergencies, including fires and earthquakes, and less critical events, such as power failures. Fire-detection systems include electronic heat and smoke detectors that can activate audible alarms and automatically notify local fire departments. For fire suppression, hand-operated fire extinguishers and, often, building sprinkler systems are provided. Smoke is as dangerous as fire, so protective measures include the automatic shutdown of ventilating systems and elevators and the division of the building into smokeproof compartments. Occupants evacuate through protected exits (which include exit corridors and stairways in smokeproof enclosures in multistory buildings) leading to the exterior.