Commercial Low Profile Air Curtains offer length, heating options.

Available with single-length construction up to 10 ft, Commercial Low-Profile 8 (CLC08) Series provides environmental separation, flying insect control, and indoor air comfort at open retail, institutional, and commercial front doorways. Standard options include

[source: http://news.thomasnet.com/fullstory/Commercial-Low-Profile-Air-Curtains-offer-length-heating-options-20041361]