The doors are a scientific effort to equalize air pressure. Revolvers, as they are known in the industry, prevent the city's skyscrapers from turning into highrise wind tunnels. When cold weather sets in, for example, and a skyscraper's heaters are turned on, hot air rises to the top of the building, leaving a vacuum on the lower floors. If a regular swinging door, or swinger, is opened, cold air is sucked in to fill that void, creating winds that muss hairstyles and blow papers around lobbies.
from Saturday's NYTimes.