Curved glass revolving doors help maintain a constant indoor temperature while providing secure and orderly entrances and exits. Revolving doors use bent glass to provide an environment of elegance and a feeling of order and security.
A bent or curved glass revolving door typically consists of three or four doors that hang on a center shaft and rotate around a vertical axis within a round enclosure. Revolving curved glass revolving doors are energy efficient inasmuch as they prevent drafts, thus preventing increases in the heating or cooling required for the building. At the same time, curved glass revolving doors allow large numbers of people to pass in and out. Around the center shaft of the revolving door there are usually three or four doors called "wings" or "leaves." Large diameter curved glass revolving doors can accommodate strollers and luggage racks. The tallest curved glass revolving door currently is approximately 16 feet (4.9 m) high with 4 wings.
The curved glass revolving doors allow people to see and anticipate each other while passing through the door. Manual curved glass revolving doors rotate with push bars causing all wings to rotate. Curved glass revolving doors typically have a "speed control" (governor) to prevent people from spinning the doors too fast. Automatic curved glass revolving doors are powered above/below the central shaft, or along the perimeter. Automatic curved glass revolving doors have safety sensors; but there has been at least one fatality. Skyscraper design requires some sort of draft block, such as curved glass 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 due to convection. Modern versions permit the individual curved glass revolving doors of the assembly to be unlocked from the central shaft to permit free flowing traffic in both directions. The curved glass revolving doors are always closed, so wind and drafts cannot blow into the building, also efficiently minimizing heating and air conditioning loads. In right hand traffic countries, curved glass 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, revolving doors should revolve clockwise, but they do not always. Curved glass 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.
Sometimes a curved glass revolving door is designed for one-way traffic. An example is the now-common usage in airports to prevent a person from bypassing airport security checkpoints by entering the exit. Such curved glass revolving door are designed with a brake that is activated by a sensor should someone enter from the incorrect side. The door also revolves backwards to permit that person to exit, while also notifying security of the attempt.