The invention relates to a dryer for drying fuel materials such as wood bark, wood chips, sludge, garbage, peat moss or the like. In a preferred embodiment the dryer comprises a conveyor, consisting of twin endless belts, which carries the material to be dried along a vertical path defined between parallel runs of the endless belts, and ductwork which serves to direct heated air (received from any appropriate source) across the vertical path to remove moisture from the material as it is being conveyed. The ductwork includes at least one feed duct for use in delivering the heated air to one side of the vertical path, and at least one exhaust duct for use in withdrawing moisture-laden air on another side of the vertical path. Suction is applied at the exhaust ducts to draw drying air through the ductwork, and the feed and exhaust ducts are made to seal against the conveyor to reduce the introduction of ambient air into the dryer ductwork under the suction applied.