Wet filters operate in accordance with the principle of the absorption, according to which the abatement of the vapors of polluting substances and of the solid particles present in a gaseous flow take place through their transfer in a given fluid absorbent.
The absorption can be a purely physical phenomenon, in which case the substance dissolves in the liquid, or chemical when the substance reacts in the liquid phase with a specific liquid or with suitable reagents dissolved in it. The transfer of pollutants from the gas phase to the liquid is by diffusion, while, for the particulate matter, more simple phenomena of physical aggregation are involved.