A pollution control unit comprises a tank naving an outlet and an inlet for gases treated therein. A pair of spray compartments are spacedly situated within the tank, and a de-entrainment compartment is situated between the spray compartments. A series of spaced baffles define the spray and de-entrainment compartments and in addition define the flow path of the gases serially through the compartments. Spray devices are provided for directing water sprays into the gases but only within spray compartments. Additional spray and de-entrainment compartments are contemplated