Embodiments of mechanisms of an air treatment system are provided. The air treatment system includes a heating tank having a heating chamber containing air. The air includes gas, water vapor, a number of contaminants floating thereon. The air treatment system further includes a cooling tank having a first cooling chamber receiving the air from the heating chamber. Some of the water vapor in the first cooling tank condenses to a number of droplets, and some of the contaminants are mixed with into the droplets.