For commercial applications like store entrances, user comfort dictates low face velocities, which reduce effectiveness of separation of exterior air from interior air.

NIS Systems Co. is a world's leading designer and manufacturer of process air-curtains and environmental air barriers for a variety of industrial process applications. For special applications Canadian Air Systems offer high volume and high penetration tangential air curtains with highly laminar airflows.

An air door or air curtain is a device used for separating two spaces from each other, usually at the exterior entrance. The most common configuration for air curtains is a downward-facing blower fan mounted over an opening. Normally this opening is an entrance to a building, and the air curtain is intended to help keep flying insects out by creating forceful turbulence. It also helps keep outside air out, avoiding cold drafts by mixing-in warm air from the air curtain. The fan must be powerful enough to generate a jet of air that can reach the floor.

The most effective air curtain for containing heated or cooled air inside a building with an open door will have a high face velocity at the opening, generated by top-down flow, recovered by a recirculating air plenum and duct return to the source fans. This configuration is available for new construction, but difficult to provide in existing buildings. The air curtain is most effective with low exterior wind velocity. At higher wind velocities, the rate of air mixing increases and the outside air portion of the total face flow increases. Under ideal conditions of zero wind, the effectiveness of the air curtain is at its maximum.

Non-heated air curtains are often used in conjunction with cold storage and refrigerated rooms. Airflow through a door depends on wind forces, temperature differences (convection), and pressure differences.

Air curtains can be used to save energy by reducing the heat transfer between two spaces, although a closed and well-sealed physical door is much more effective. A combination is usually utilized; when the door is opened air curtain turns on, minimizing air flow from inside to outside and vice versa.

Properly installed air curtains cut cold air loss and reduce humidity, thus reducing the load on refrigeration or air-conditioning plant and thereby saving energy by reducing compressor running time, maintenance, gas and recharging intervals. These units are an alternative to fast-acting roller doors and PVC slat curtains, and can be situated above or to the side of industrial doorways to create a powerful seal across the opening, keeping cold air in while providing complete visibility and access. This means that forklift drivers don't have to get out of their cabs to open and close doors so that moving from one area to another is a lot easier and productive. Unlike plastic slat curtains, which quickly become opaque with use, an air curtain provides 100% visibility at all times. Units have been installed in loading bays, factories, hangars and production facilities, such as food processing and pharmaceuticals, where differential temperatures are encountered overseas.

Insect an pest control a benefit

An air curtain supplying a high-velocity sheet of air across a door opening will prevent flies and other flying insects from entering a building. This is particularly important in restaurants and bars, and any premises where food is manufactured or served - where strict environmental health regulations apply. It is an extremely beneficial side effect as an air curtain is primarily employed for climate control yet units are also installed overseas for insect control alone.