Abstract: A gas purifying apparatus, including: at least one cylindrical ground electrode configured to receive gas flowing therethrough; a discharge electrode disposed centrally within each of the at least one cylindrical ground electrode; and a power supply electrically connected to the discharge electrode and the at least one cylindrical ground electrode so as to produce an electric field and a corona discharge from the discharge electrode to a corresponding cylindrical ground electrode to generate ions and free electrons into the gas to ionise substances in the gas for gas purification, wherein the discharge electrode and the corresponding cylindrical ground electrode form at least one plasma chamber when power from the power supply is applied, and wherein the discharge electrode includes: at least one annular plate having an outer edge extending towards the corresponding cylindrical ground electrode.