Air door

The most common implementation is a downward-facing blower fan mounted over an entrance to a building, or over an opening between two spaces conditioned at different temperatures.

They can be used to help keep flying insects out by creating forceful turbulence, or help keep out outside air, thus reducing infiltration through the opening.

There are some studies in the scientific literature that present analytical methods to predict the sealing efficiency obtained with an air curtain.

[4] Following the COVID-19 pandemic, groups have been researching the use of air curtains for preventing the spread of viruses in enclosed areas such as hospital wards.

[6] Such devices aim to use air curtains to protect healthcare workers from airborne viruses such as coronaviruses.

Air doors work best when the pressure differential between the inside and outside of the building is as close to neutral as possible.

They are intended to be installed at doorways having low pedestrian traffic where the door is mainly closed, and are useful in providing warmth.

The main differences are: Air curtains consume electrical energy during their operation, but can be used for net energy savings by reducing the heat transfer (via mass transfer when air mixes across the threshold) between two spaces.