Emergency Responders: Collapsed structures are a common result of earthquakes. Rescue workers and emergency responders may have to enter collapsed structures to perform search and rescue activities, and it is vital that they perform their duties safely. What is a collapsed structure? When internal load bearing structural elements fail, a building will collapse into itself and exterior walls are pulled into the falling structure. This scenario may be caused by construction activity, an earthquake or fire and may result in a dense debris field with a small footprint. Alternatively, if the structural failure is caused by an explosion or natural forces such as weather, the building may collapse in an outward direction resulting in a less dense and scattered debris field. Who enters a collapsed structure? Following a catastrophic failure of a structure, rescue workers and emergency responders may be required to enter the collapsed structure. Emergency responders include firefighters, police, emergency medical technicians, construction workers and government representatives. Emergency responders may be responsible for assisting survivors, extinguishing fires, shutting off utilities, assessing structural instabilities, shoring-up safe paths into the structure and assessment of other hazards such as airborne contaminants. Rescue workers such as Urban Search and Rescue Teams focus on finding survivors and later removing victims from collapsed structures. See more from topic source: https://www.osha.gov/html/a-z-index.html