This fire curtain located on the first floor of the Schaffer library atrium, comes down automatically during the rare event of a fire emergency. The smoke detectors activates the door, and you can see the speed at which the door comes down.
It's important to note where the emergency exits are located throughout the library, as most people will initially head towards the front main entrance creating a bottleneck. For instance, if you happen to be in the Lally Reading Room on the opposite side of the fire curtain and it comes down, there are emergency exits in the back.