Rapid digestion of plant tissue using sulfuric acid results in emission of large quantities of SO3fumes. These fumes are a serious hazard to personnel and cause corrosion of equipment and exhaust ducts. A simple apparatus was designed for effective fume control during plant tissue digestion with sulfuric acid using a heating block. The apparatus consists of a battery of reflux columns that can be installed as a unit on top of the digestion tubes after they have been placed in the heating block. The apparatus is very economical to construct.