Foodservice operators typically use air curtains, or air doors, in a variety of door openings to control temperatures, repel insects and mitigate odors and smoke. These are most often installed above dock doors, in walk-in cooler doors and at drive-up windows.
Air curtains consist of a strong fan that creates an invisible air barrier to effectively separate one environment from another. The unit pulls in conditioned air, accelerates it and forces it through the air curtain. Discharged air hits the floor and is directed outward.
These systems can be utilized with plastic strip doors or swinging plastic doors at the entrances of walk-in coolers and freezers or on front-of-the-house reach-in coolers. This helps keep food in the cooler at safe temperatures while maintaining the temperature of the surrounding area.
Air curtains keep temperatures regulated in other applications, such as at back receiving doors, dock/warehouse doors and drive-thru windows; by patios; over indoor and outdoor bars; and at customer entrances. This compensates for cold or hot air coming in, which helps the HVAC system work more efficiently. When negative air pressure is strong, air curtains also can be used in conjunction with makeup air fans.
Most foodservice air curtains fall into two categories, climate control and insect control. Climate control air curtains are used on the front of facilities to keep temperatures separated. This helps increase customers’ and employees’ comfort levels. In the back of the house, insect control air curtains help keep exterior elements and insects from entering sensitive kitchen environments. This type traditionally uses higher velocity motors to keep insects from intruding.
Most air doors require between 115 and 480 volts to operate. Optional heating functions are powered by gas, electricity or steam. Air velocity ranges from 1,800 up to 5,100 feet per minute. Single- and dual-speed models, with either remote or automatic switches, are available. Motors range from 1/5 to 20 HP.
Air curtains can be mounted either horizontally above doors to blow air down or vertically on the door’s side, which blows air across.
These systems typically come in full foot–width increments from 3 feet all the way up to 30 feet wide, but in the foodservice industry, units are typically 36, 42, 48, 60 and 72 inches wide.
Air curtains have a steel or stainless steel cabinet, include galvanized blower wheels and are usually one-piece construction for easy installation. Plastic and powder-coated covers also are available. Designs range from a basic industrial type for the back of house and loading docks to more architectural, aesthetically pleasing models for the front of house.
The critical specifying considerations are uniformity, noise levels and construction. Uniformity is critical to making sure the entire opening is uniformly covered with the air curtain and limited or no gaps in air flow are felt. Noise levels are another consideration, since loud air curtains often disrupt communication in customer and kitchen environments. Construction is also important as stainless steel units are more durable and aesthetically pleasing in foodservice environments.
Most air curtains include the unit and some method of activation, whether it is an on/off switch or an automatic door switch that activates the air curtain when the primary swinging or sliding door opens.
For cold weather environments, electrically heated air curtains can be used to warm the air as it comes out of the nozzle, generating supplemental heat for people around the door opening. This creates a more comfortable environment.
Innovations include electronic controls on heated units that automatically adjust to temperature needs and space.
Other features include automatic thermal overload that protects the motor from burnout, washable air filters and high-efficiency air filters that remove airborne contaminants.
Like electric air curtains, vinyl curtains limit the release of cold air as well as keep out insects. These curtain strips are most often used with walk-ins, are inexpensive and generate a return on investment in three to four months.
Vinyl curtains can be customized to fit any size door opening, although the most common is 38 inches wide by 84 inches high. The strips can be easily trimmed with scissors.