The interaction of the end of the vent tube and the surrounding air is of great importance for providing efficient ventilation of rooms. Sometimes, special devices or even electric fans are installed on the ventilation tubes facilitating the air motion in them.
One can see several rotating ball-shaped blade wheels almost on every house in South Korea. Each of them crowns the ventilation tube and is a very simple and effective exhauster.
The rotator is attached to the ventilation tube with the aid of light bearings. Its blades are installed so that even a gentle breeze can rotate them. The blades that move circlewise spin the air inside the sphere. The centrifugal force acts on the air molecules and throws the air out with force thereby providing rarefaction at the tube end and active entry of the air evacuated from the room. 

Dynamization of air in the tube exit area provides effective ventilation.