Abstract: A device is disclosed for treating exhaust gases from an internal combustion engine having a gas inlet adapted to be connected to the exhaust of the internal combustion engine and a plurality of serially arranged interconnected reaction chambers. The first of the chambers is connected to the gas inlet and includes a gas outlet forming a gas inlet into a second chamber. The second of the chambers has a gas outlet forming a gas inlet with a third chamber, and so on. The last reaction chamber has a gas outlet to atmosphere. A perforated gas deflector plate is mounted transversely of the path of gas flow in alignment with each outlet of the reaction chambers and spaced inwardly into the reaction chamber associated with the outlet. Means are provided for spraying purifying fluid containing an aqueous solution of sodium percarbonate and sodium bicarbonate into each reaction chamber and drain means associated with each reaction chamber draining the remains of the aqueous solution from the housing.