The purpose of the fresh air project is to maintain the indoor temperature, humidity and other conditions remain unchanged, increase the supply of fresh indoor air to improve indoor air quality and prevent the spread of viruses. Fresh air projects usually use equipment such as fresh air machines, air supply ducts, filters, etc., to introduce fresh air into the room and exhaust indoor waste air. The design and construction of fresh air project need to fully consider the construction of the building, space layout and the use of the scene and other factors, the project classification is mainly divided into residential, commercial, office, etc., the application of a wide range of scenes.