Scrubber systems are a diverse group of air pollution control devices that can be used to remove some particulates and/or gases from industrial exhaust streams. Traditionally, the term "scrubber" has referred to pollution control devices that use liquid to wash unwanted pollutants from a gas stream.

Recently, the term is also used to describe systems that inject a dry reagent or slurry into a dirty exhaust stream to "wash out" acid gases. Scrubbers are one of the primary devices that control gaseous emissions, especially acid gases. Scrubbers can also be used for heat recovery from hot gases by flue gas condensation. Air scrubbers are commonly used in process-air applications to eliminate potentially harmful dust and pollutants. A liquid, in general water added with active chemicals adapted to the process, is sprayed in to the air flow. Aerosol and gaseous pollutants in the air stream are removed by either absorption or chemical reactions with the water solution. 

A schematic drawing of a typical spray nozzle scrubber configuration is shown below. 

Water with chemicals are sprayed with high pressure through nozzles into the air flow. Some of the water evaporates, especially if the process-air is hot, and disappear with the exhaust. Water droplets are separated from the exhaust and re-circulated back to the water reservoir. Evaporated water is replaced by fresh water and chemicals. Dust and pollution products from the process are removed periodically through the drain.