Building and fire codes require a specific number of exit doors out of every occupied portion of the building. In most cases, at least two exits out of each room is required. Many times, doors are installed specifically as "emergency exits", and are used for no other purpose. Exit doors must allow exit at all times and therefore must be kept unlocked in the direction of exit. Exit doors, however, can often create a security weakness especially if the door is located away from typical traffic.
To remedy this issue, emergency exit doors are often equipped with "exit alarms" and will cause an audible alarm to sound when the exit door is opened. Giving a typical delay of 15 seconds from when the alarm sounds to when the door will physically open. This allows management to get to the door before an individual exits the facility.