The Furnace treats the output matte from the smelter. The off-gas temperature of the furnace runs up to 1,200 °C. The off gas is cooled by an evaporative cooling tower to around 270 °C. The off-gas ducting is water cooled up to the evaporative cooling tower where the cooling tower is brick lined because of corrosion. Due to over spray caused by lances injecting an air-water mixture, acid forms on the water-cooled tubes. The duct is brick/refractory lined.