emergency exit

An emergency exit (also known as a fire exit) is a special exit used during emergencies in a building or other structure such as fires. The combined use of regular and emergency exits allows for faster evacuation, and emergency exits provide alternative means of evacuation if regular exits are inaccessible.
Emergency exits must:

Be clearly marked (usually with signage that is normally illuminated, or is illuminated by a backup power source if central power fails)
Be in easily-accessible locations
Direct people to safe areas (usually outside)
Be regularly maintained and free of obstructions (they may not be used for storage)
Be secured to prevent unauthorized entry during normal operations
Open in the direction of escape
An emergency exit's path usually ends in an outward-opening door with a crash bar with exit signs pointing to it. It is usually a door to an area outside of the building, but may also lead to an adjoining, fire-isolated structure with clear exits of its own.
A fire escape is a special kind of emergency exit consisting of stairs and/or extendable escape ladders mounted on the outside of a building.

View More On Wikipedia.org