Revolving door

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 (via acting as an airlock), 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.

Around the central shaft of the revolving door, there are usually three or four panels called "wings" or "leaves." Large diameter revolving doors can accommodate strollers and wheeled luggage racks. The tallest revolving door in Europe is currently 5.2m high with 4 wings.

Some "revolving door displays" incorporate a small glass enclosure, permitting small objects such as sculpture, fashion mannequins, or plants to be displayed to pedestrians passing through. Such enclosures can either be mounted at the central pivot, or attached to the revolving door wings.

The wings of revolving doors usually incorporate glass, to allow people to see and anticipate each other while passing through the door. Manual revolving doors rotate with pushbars, causing all wings to rotate. Revolving doors typically have a "speed control" (governor) to prevent people from spinning the doors too fast.

Automatic revolving doors are powered above/below the central shaft, or along the perimeter. Automatic revolving doors have safety sensors, but there has been at least one fatality recorded.

Skyscraper design requires some sort of draft block, such as revolving doors, to prevent the chimney effect of the tall structure from sucking in air at high speed at the base and ejecting it through vents in the roof while the building is being heated, or sucking in air through the vents and ejecting it through the doors while being cooled, both effects due to convection. Modern revolving doors permit the individual doors of the assembly to be unlocked from the central shaft to permit free flowing traffic in both directions, but this feature is typically used only during emergencies, or to admit oversize objects. Normally, the revolving door is always closed so that wind and drafts cannot blow into the building, to efficiently minimize heating and air conditioning loads.

In right hand traffic countries, revolving doors typically revolve counter-clockwise (as seen from above), allowing people to enter and exit only on the right side of the door. In left hand traffic countries such as Australia and New Zealand, revolving doors revolve clockwise, but door rotations are mixed in Britain. Direction of rotation is often enforced by the door governor mechanism, or by the orientation of the door seal brush (weatherstrips).

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Wikipedia