The roof access doors had to be left unlocked. If they were connected to a buzzer system, they were supposed to be fail-safe—meaning that they would automatically unlock if power failed or calamity struck. The trade center, however, was exempt from the code. The Port Authority had decided to lock the doors and the Fire Department had chosen to go along with that decision, believing that such a policy would reinforce its message that down was the proper way to evacuate in a high-rise fire. As a result, three sets of doors blocked access to the roof in each tower.
