It’s a first world problem, for sure, but who would have guessed that weird gust of wind you feel when you walk into a store or business or restaurant actually serves a purpose other than to be loud and mildly annoy you?

(I mean, outside of restaurant owners. And the people who make the things. And, I guess, probably anyone who isn’t me.)

Yep, it turns out those huge hanging door fixtures are called “air doors” or “air curtains” and they’re meant to keep the bugs out. According to air door company Berner International, the first U.S. patent for air doors was issued in 1904 to Theophilus Van Kemmel and the invention grew in popularity in Europe throughout the late 1940’s and 1950’s – presumably after people started taking regular baths and actually caring whether or not bugs were around.

By channeling air through a powerful, directed nozzle, air doors are able to form an invisible barrier against dirt and insects without impeding regular business traffic. They’re also a cheap way to regulate a place’s internal temperature by serving as an effective shield against the incoming flow of hot air or cold air or other such unpleasantness.

So in sum: Science! And invisible force fields.

You may now return to your regularly scheduled programming.

PicThx Door Air Curtain