Why Air Structures Use Revolving Doors

Why Air Structures Use Revolving Doors

Sometimes, the simplest designs and ideas are the best ones—the revolving door might be more interesting than you expect. An air supported structure or dome wouldn’t be much without an entry system that lets people in easily, while making it difficult for the enclosed air to escape. Most inflated bubble structures, therefore, make use of the common revolving door.

Revolving doors have changed a lot over the years, but the principle has remained the same. The revolving nature of the door allows the movement of people or things in and out of a building, while limiting the flow of air. Although perfect for the task, they weren’t originally conceived for air supported structures.

The first patent for a revolving door was given to H. Bockhacker of Berlin, Germany—all the way back in 1881. A US patent for a revolving door was issued not long after to Theophilus Van Kannel in 1888.

Theophilus’ patent explained why a revolving door might be better than a typical swinging door. With a seal, the door "possesses numerous advantages over a hinged-door structure… it is perfectly noiseless ... (and) effectually prevents the entrance of wind, snow, rain or dust…"

Despite its obvious benefits, Theophilus’ “storm-door structure” may have also had an ulterior motive. It seems that Theo’s social anxiety may have inspired his invention. His idea for a door that you wouldn’t need to hold open for another person may have been his solution to avoiding an anxious encounter .

Since its invention by Van Kannel, revolving doors have seen steady use in construction because of their ability to control air flow and cut costs of heating and cooling, as well controlling access to a building. Because of their utility, revolving doors have also had some unique uses.

The tallest revolving door in the world is located, not surprisingly, on the tallest free-standing structure in the world: Dubai’s Burj Khalifa tower. This tower is a staggering 829.8 meters tall—for reference, North America’s tallest freestanding structure is Toronto’s CN Tower at 553 meters. The revolving door, located at the observation deck 555 meters up, deals with the unforgiving wind that blasts the building at such an altitude. At this incredible height, the doors need to be able to withstand winds equivalent to an F3 class tornado!

Revolving doors are a fantastic design. A simple and elegant solution that just works.

Revolving doors have been a part of air structures since their outset. Air domes have the unique limitation that movement of air in and out of the structure needs to be carefully controlled. Air locks and revolving doors do exactly that. Revolving doors prevent the flow of air out of the structure, but keep the structure completely accessible.

Because revolving doors are so established, most people use them regularly. Couple this with the fact that revolving doors are nearly impossible to use incorrectly and the air stays where it needs to be, inside the bubble.

When H. Bockhacker and Theophilus Van Kannel developed their revolving door systems, it’s unlikely they imagined anything as fantastic as an inflatable air supported structure, but thanks to them, these types of structures are a reality. The next time you’re entering a soccer dome or tennis bubble, take a minute to appreciate the genius that is the revolving door!