Communication: A corona discharge reactor consisting of a hollow needle cathode and a stainless steel net anode was used to remove benzene, toluene, and chlorobenzene in a synthetic air stream. Two gas flow directions (upflow and downflow) were adopted to examine the contributions of the separated reaction zones, a high-energy corona zone at the needle cathode tip and a relatively large zone outside it. It was observed that the removal efficiency of the three target components did not depend on the gas flow directions.