The air curtain is a device which creates a flow of air separating two spaces, usually found at an exterior entrance to a property. Also known as an ‘air door,’ the most common set up involves a downwards facing air blower mounted over the opening entrance, blowing air vertically across the area. They can be either heated or cooled. Whichever style is used, the fan component within the device must be strong enough to create a jet of air capable of reaching the floor.
Generally, the air curtain is a multifunctional device providing several important services to the building. Firstly, they create a significant amount of forceful turbulence in the area, restricting the entrance of flying insects and airborne pests into the building. They also help minimise the possibility of infiltration through the exterior opening, keeping outside air where it is supposed to be and preventing loss of conditioning. It is a viable system of avoiding the creation of cold drafts, mixing in the warm air generated by the air curtain itself to sustain the comfortable temperature whilst the door or access is opened. They can help to reduce energy costs, preventing loss of regulated air when the door is open. They are most commonly found at customer entry ways, but also in industrial spaces, hangars, cargo entrances and delivery access areas.
It is thought that an efficient air curtain device will have covered its costs within two years of installation by reducing the strain on the heating system or air conditioning within the building, decreasing energy bills accordingly. In most cases, a mechanism such as a door switch is what turns the unit on and off again so that it is only functioning when necessary, further saving energy. Heated air curtains provide additional heat to an entrance space, preventing the wind chill effect from the opening when faced with chilled outside air, particularly in cool climates. The air curtain is most effective when there is minimal pressure difference between the interior and exterior, or in fact where there is neutralised pressure differentiation. Changes in pressure, very extreme differences in the interior and exterior temperature and high levels of humidity can make the air curtain less effective. Exterior wind conditions can also have detrimental effects on the success of the air curtain. In stronger winds, there is an increased rate of mixing between the interior and exterior air and the effectiveness of the barrier is minimised. Air curtain technology can still be used in windy areas, but are often chosen for their benefits in minimising infiltration rather than stabilising temperatures.