Stragely enough, I had to open an emergency door a couple of weeks ago. It was in a well known bank who had the main Chubb door unlocked but would not open. Although there was an emergency door with two combinations locks on, the staff did not have the combination numbers to unlock it !!!!
Luckily, after a few mins, I managed to get the main door open and could then access the inside of the vault. Having done this, the emergency door could then be accessed and I opened the door by manipulating the combinations to open after removing the lock cover plates. This emergency door was exactly the same construction as the main door but obviously a lot smaller. There was also on the inside of the vault access hole, a very strong grille gate secured by a double keyed Chubb lock. Very glad that I managed to get the main door open or this could have been a bit of a nightmare !!!