A revolving door typically consists of three or four doors that hang on a central shaft and rotate around a vertical axis within a cylindrical enclosure.
Revolving doors are energy efficient as they prevent drafts (thanks to acting as an airlock), thus preventing increases in the heating or cooling required for the building.
Another plus for revolving doors is that they allow several people to pass in and out at the same time.
Revolving doors can also be used for security; they help restrict entry to a single person at a time if the spacing between the doors is small enough. This is in contrast to a normal door which allows a second person to easily “tailgate” an authorized person. Extreme security can call for bulletproof glass.
Moreover, revolving doors can optionally be equipped with a wide range of features to meet customer requirements, such as the emergency exit function, integration of a manual or motorized nighttime closure, and many more.