Many building codes dictate the type of locks that can be used on any type of emergency door or fire exist. Most building codes do not allow for additional locks to be placed on doors with a panic bar or emergency exit device. Placing a chain or latch on the door in order to lock it is a violation of most building codes.
For emergency exits, there are three general types of hardware and locks which can be installed in compliance with building and fire safety codes. These are free egress, delayed egress and controlled egress.