A exhaust fan pulls air out of a building and forces it into the room. This causes a positive pressure differential in the room forcing air out through the gable and/or soffit vents, while at the same time producing a negative pressure differential inside the living areas which draws air in through open windows.

Normally, with exhaust fan, the air change efficiency can reach up to 90%-97%. So exhaust fan are widely use industry & agriculture, such as heat treatment plant, casting plant, plastics plant, aluminum plant, electroplating plants, chemical plants, greenhouses, livestock farms, garment factories, etc.