Types: Air curtains and doors are usually divided into two categories: those that recirculate air from the interior of an establishment and those that do not. Recirculating air doors are designed to prevent the loss of heated and cooled air, thus maintaining an operation's interior temperature. Commercial establishments where doors need to be left open tend to be the primary users of these products. Non-recirculating air doors separate two environments and/or prevent flying insects from entering a foodservice facility. Operators can apply such units to openings as various in size and purpose as drive-thru windows and loading docks. Air curtains can also work in conjunction with plastic strip doors or swinging plastic doors; oftentimes used at the entrances of walk-in coolers and freezers. Another option is to position air curtains on front-of-the-house reach-in coolers. These air curtains help keep food in the coolers at safe temperatures while maintaining the temperature of the surrounding area.
Capacities/Footprints: Air curtains, mounted above a door either on the interior or exterior, are available for doors from 36" to 12" wide, and can now be custom-manufactured for doors up to 16" wide and 20" high.
Energy Source(s): Most air doors require between 120 volts and 480 volts to operate. Gas, electricity or steam can power the optional heating function most units feature.
Standard Features: Air doors create an invisible air seal generated by high-efficiency, direct-driven centrifugal fans that compress air inside the unit and release it through a directional nozzle outlet with a pressure designed to be powerful enough to stop winds up to 25 mph. An air curtain used for repelling flying insects requires a higher velocity of air than one designed for environmental preservation.
Optional Features: Air curtains are available with adjustable air velocities and operators can purchase them unheated or equipped with electric, steam or hot-water heating units. Industrial models are available with gas-fired heating options. In certain cases, an air-door system must be hung from a ceiling, regardless of the opening it will shield. When such a situation arises, manufacturers offer special bracket systems for installation. Units can also be equipped with separate control switches that can determine a system's thermostat and air pressure, among other factors. For facilities prone to vandalism, such as schools and prisons, some air-door systems come with tamper-resistant features. An automatic door switch can control operation of an air curtain when a door opens. Air curtains in high traffic areas can come with a time delay control.
If an air curtain is installed over a sliding door, such as those found in many drive-thru windows, an automatic roller-door switch will turn the air curtain on when someone opens the window, and off when the window closes. Similar switches are available for hinged doors as well. Experts do not recommend combining such features with air doors equipped with heating systems. The amount of time such systems would be active is limited, thus rendering the heating process ineffective.
New Features/Technology/Options: For front-of-the-house applications, manufacturers now offer air doors that house all their internal components above the ceiling. Such units are designed for operations that pay particular attention to their interior design.
Prime Functions: Air curtains keep two environments separate by preventing the intrusion of flying insects, dust and other airborne contaminants and by keeping inside conditioned or heated air untainted by outside air. For optimum protection, an environmental control unit should be mounted on the interior of a doorway, drawing in conditioned air through an intake screen and discharging it through a nozzle to create the necessary air seal. Air curtains also facilitate free-flowing traffic in facilities, as well as unobstructed vision. In addition, some operators now use air curtains to separate smoking and non-smoking areas inside their facilities. While air curtains and doors can and do serve multiple functions, units can be ordered with particular features and installed at a wide variety of angles to make them more effective for specific applications. For example, an air door that is primarily intended to prevent pests from entering a facility should blow air at a higher velocity than other units, and should be installed at an angle that allows it to blow outward.
Key Kitchen Applications: Air curtains control insects and aromas and regulate temperatures in kitchens, as well as above dock doors, walk-in coolers, drive-up windows or any opening susceptible to energy loss or temperature variation. Specialty units are available that surround large pieces of cooking equipment, such as conveyor ovens. These contain the units' heat, thereby making the kitchen environment more pleasant for staff.
Purchasing Guidelines: With food safety a widespread concern, operators may use air doors and curtains to help reduce the risk of foodborne illness by preventing insects from entering a kitchen or dining area. Because they can help maintain heated or conditioned air temperatures, air curtains and doors also offer operational savings and can pay for themselves in as little as two years. When installing an air curtain, operators should take into consideration its location in relation to staff and, especially, the front of the house. This is because different units have different noise outputs, which can affect an operation's atmosphere and customers' dining experiences.
If operators plan to access a walk-in cooler frequently, they should consider adding an air curtain and strip door. Doing so prevents cooled air from escaping, which will lower energy costs and extend compressor life. Units that draw air from inside a building but expel some air outside can create what is called “negative pressure,” which can make opening doors difficult.
Customer entrances should not be equipped with high-velocity air-door systems, as they can create an unpleasant entrance. Systems installed at customer entrances should include a heating function that can be turned on during colder weather.
Maintenance Requirements: For best performance, regularly clean air curtains and plastic strip doors used in conjunction with them. Air-cleaning filters are available for many air curtains. These filters, which are often constructed of washable aluminum mesh and are hence reusable, offer the benefits of both improving air quality and reducing odors.
Food Safety & Sanitation Essentials: Air curtains repel houseflies and other pests, helping to eliminate potential exposure to diseases. The FDA specifically recommends the use of air curtains for the exclusion of insects. Several states have additionally enacted legislation regarding the mandatory installation of air curtains at specified openings in food production facilities.