Have you ever been sitting in a restaurant, minding your own business and eating your meal, and a fly buzzes in when the server opens the door to the outdoor patio seating? There are reasons why you aren't sitting outdoors and flies are one of them.
There are 6 good reasons why engineers and restaurateurs should strongly consider including air curtains in restaurant design.
Check out this blog post by Schwank Innovative Heating Solutions: https://www.patioschwank.com/6-reasons-why-you-need-air-curtains-in-your-restaurant/