An air door or air curtain is a device used to prevent air or contaminants from moving from one open space to another. The most common use is a downward-facing blower fan mounted over an entrance to a building, or an opening between two spaces conditioned at different temperatures.
Used in applications when there is a need to create an invisible barrier to control temperature. Such as preventing loss of cool air during cooling and warm air during heating. Air curtains for restaurants have other benefits such as blocking out exhaust fumes, smoke, odours and insects.