Methods and apparatus for treating an exhaust gas in a foreline of a substrate processing system are provided herein. In some embodiments, an apparatus for treating an exhaust gas in a foreline of a substrate processing system includes a plasma source coupled to a foreline of a process chamber, a reagent source coupled to the foreline upstream of the plasma source, and a foreline gas injection kit coupled to the foreline to controllably deliver a gas to the foreline, wherein the foreline injection kit includes a pressure regulator to set a foreline gas delivery pressure setpoint, and a first pressure gauge coupled to monitor a delivery pressure of the gas.