Abstract: Apparatus for treatment of exhaust gas from internal combustion engines, for use in underground mine workings, comprises an exhaust pipe with a water jacket, and a conditioner chamber retaining a bath of water through which the exhaust gas flows in passing through the inlet to the outlet of the chamber, the chamber further including means for condensing water vaporized from the bath by passage of exhaust gas therethrough and for discharging such condensed water back to the bath. The apparatus may include a heat exchanger upstream of the conditioner chamber and containing a system of plates or webs which sub-divide the gas flow path through the heat exchanger into passageways, the plates or webs being connected to the inner wall of a water jacketed casing of the heat exchanger.