Air Curtains:- 

Air Curtains, maintains the interior air conditioning efficiency to save energy, while preventing the entry of dust, harmful insects and fumes from outside. An air curtain is a device used for separating two spaces from each other. It usually happens at the exterior entrance. The most common configuration for air curtains is a downward facing fan mounted over an opening. Normally this opening is an entrance to a building and the air curtain is intended to help keep outside air out and avoid cold draught by mixing in warm air from the air curtain. The fan must be powerful enough to generate a jet that can reach the floor.