Natural disasters such as earthquakes, floods and mudslides are among the most common causes of a building being red- or yellow-tagged. Usually, after such incidents, the local government body responsible for enforcing the building safety code examines the affected structures and tags them as appropriate.
In some areas of the United States, buildings are marked with a rectangular sign that is red with a white border and a white "X". Such signs provide the same information as "red-tagging" a building. Tagging structures in these ways can warn firefighters and others about hazardous buildings before the buildings are entered.