Abstract: A system for treating and removing toxic by-products of semiconductor plasma etching processes utilizes a collection box having various treatment chambers in seriatim. A heated inlet conducts a vaporous process stream into an expansion chamber where the gas is expanded. The expanded gas flows over a baffle weir into a packing chamber filled with plastic media spheres. In the upper reaches of the packing chamber but below the weir top, a deionized water atomizer sprays deionized water to humidify and cool the expanded gases which allows the water soluble toxic by-products, such as aluminum trichloride, to initially precipitate out and condense on the spheres. With continued water flow the by-products solubilize in the water and flow to an acid drain. Remaining vaporous gaseous exhaust products pass under a weir defining one side of the packing chamber up to an exhaust chamnber where a series of inclined staggered baffles and a strainer trap remove water from the gaseous exhaust and return it to the acid drain.