A Automatic Revolving Door typically consists of three or four doors that hang on a center shaft and rotate around a vertical axis within a cylindrical enclosure. Revolving doors are energy efficient as they prevent drafts; thus preventing increases in the heating or cooling required for the building. At the same time, revolving doors allow large numbers of people to pass in and out Revolving doors can also be used as security devices to 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 require bullet-proof glass. At many banks and high security areas Automatic Revolving Door is best suited.
