A Venturi scrubber is a wet scrubber that essentially washes gases or particulates out of a gas stream. To accomplish this removal it is necessary to mix the "dirty" gas with fine droplets of the fluid used to remove them. A Venturi accomplishes this by passing the washing fluid through a tapered neck in the Venturi nozzle introducing the gas and liquid into the system. The high speed gas breaks the fluid into tiny droplets and mixes them with itself. The fluid picks up the impurities and coalesces into larger droplets which either fall out of the gas or are collected on impingement plates or packing. The purified gas leaves the system, the dirty fluid is sent for disposal or purified for reuse.

As shown in figure, a Venturi scrubber consists of three sections: a converging section, a throat section and a diverging section. The inlet gas stream enters the converging section and as the area decreases, gas velocity increases (in accordance with the Bernoulli equation). Liquid is introduced either at the throat or at the entrance to the converging section.

The inlet gas, forced to move at extremely high velocities in the small throat section, shears the liquid from its walls, producing an enormous number of very tiny droplets.

Particle and gas removal occur in the throat section as the inlet gas stream mixes with the fog of tiny liquid droplets. The inlet stream then exits through the diverging section, where it is forced to slow down.

Venturis can be used to collect both particulate and gaseous pollutants, but they are more effective in removing particles (90-99% efficiency) than gaseous pollutants (30-60% efficiency depending on the solubility of gases). To remove gases multiple Venturis can be used in series.

Simple venturis have fixed throat areas and cannot be used over a wide range of gas flow rates. Manufacturers have developed many modifications to the basic venturi design such as square throats, adjustable throats, venturi rod scrubbers, venturi movable plate scrubbers, venture scrubber with plunger, flooded elbow scrubber etc.