The CO2 system is able to detect traces of H2, O2+Ar, N2, CH4, CO, THC, C6H6 (respectively) in CO2 background gas. CO2 Chromatography System The CO2 system utilizes a high frequency discharge ionization detector in Helium (HE12) or a flame ionization detector (UFL) to detect traces of H2, O2+Ar, N2, CH4, CO, THC, C6H6 (respectively) in CO2 background gas.