A diesel emissions control system built and tested on an industrial forklift truck is described. The system utilizes a pleated media type diesel soot filter. The temperature limit of the filter material is well below the temperature of the exhaust gas. Therefore, cooling of the exhaust gas is necessary. A finned-tube heat exchanger is included in the system to cool the exhaust gas to the required level. The performance of the heat exchanger was investigated. The focus was on the fouling of heat transfer surface by soot and the corresponding decrease of the heat transfer rate. The fouling factor was found. Also, a design practice for finned-tube heat exchangers is presented and its applicability to small size mobile equipment is discussed.