Feature-based Substructure Similarity Search

Air that is desired to be examined for impurities is drawn through a concentrator comprising a cylindrical receptacle into which the air is introduced at the base portion of the receptacle in a direction tangentially of the cylindrical wall. A scrubbing liquid such as water is supplied to the receptacle and withdrawn therefrom on a continuous basis. The quantity of water only partially fills the region at the base of the receptacle where the air is tangentially introduced, with the result that the water is caused to rotate vigorously within the cylindrical wall as a thin film. The air is initially beneath the rotating film but then passes upwardly through it and is efficiently scrubbed. Gaseous and particulate impurities in the air are thus extracted into the water, and the same is drained from the receptacle and monitored for contaminant content.