Young Blonde Girl In The Room With A Chair Posing At The Door

Rotating doors
A revolving door normally has four wings/leaves that hang on a center shaft and rotate one way about a vertical axis. The door may be motorized, or pushed manually using pushbars. People can walk out of and into the building at the same time. Between the point of access and the point of exit the user walks through an airlock. Revolving doors therefore create a good seal from the outside and help to reduce A/C and heating costs climate control from the building. This type of door is also often seen as a mark of prestige and glamour for a building and it not unusual for neighbouring buildings to install their own revolving doors when a rival building gets one.
A butterfly door called because of its two "wings". It consists of a double-wide panel with its rotation axle in the centre, effectively creating two separate openings when the door is opened. Butterfly doors are made to rotate open in one direction (usually counterclockwise), and rotate closed in the opposite direction. The door is not equipped with handles, so it is a "push" door. This is for safety, because if it could open in both directions, someone approaching the door might be caught off-guard by someone else opening the other side, thus impacting the first person. Such doors are popular in public transit stations, as it has a large capacity, and when the door is opened, traffic passing in both directions keeps the door open. They are particularly popular in underground subway stations, because they are heavy, and when air currents are created by the movement of trains, the force will be applied to both wings of the door, thus equalizing the force on either side, keeping the door shut.