Fume scrubbers are light duty wet scrubbers used for air pollution control. The term “fume scrubber” was made popular by the metal finishing industry, since the pollutants emanating from the open top dip tanks were generally referred to as “fumes.” Fumes may consist of solid or liquid aerosols and / or vapors. Most of the dip tanks used in various metal finishing processes, such as anodizing, brightening, cleaning and plating, produce airborne vapors and liquid aerosols (mists).

Vapors are produced by virtue of one or more components in the bath having a high volatility, such as Hydrochloric Acid, Hydrofluoric Acid, or Ammonia. Many metal finishing processes run at elevated temperature, which increases the volatility of the bath constituents. Some compounds, such as Nitric Acid or Hydrogen Peroxide, which are non-volatile at room temperature, produce significant vapor at 140^o F.

Mists are generated either by mechanical agitation of the liquid in the bath or by bubbles forming and bursting as they escape from the liquid surface. The solution may be mechanically agitated by parts causing splashing as they are immersed and pulled out of the bath, or by intentional mixing using a circulation pump or compressed air. The formation of bubbles in solution occurs during an electrochemical process. Inevitably, some portion ranging from 5-70% of the applied amperage electrolyzes the water in the bath, causing it to dissociate into Hydrogen and Oxygen. These gases are formed in tiny bubbles that rise to the surface and burst. This mechanism for mist formation leads to a much finer aerosol than that formed by mechanical agitation.

Fume scrubbers generally incorporate nominal packed beds. They may use recycled water or water with a chemical additive such as Sodium Hydroxide. They are available in vertical counterflow or horizontal crossflow configuration. A variety of construction materials are also available, such as PVC, CPVC, Polypropylene and FRP.