tokens: The amount of N2 in LOx shall be determined by gas chromatography according to ISO 15859 - 1 Clause 7.16 . NOTE 1 CO2 can react with N2H4 to form carbazic acid ( NH2-NH - COOH ) . The carbazic acid , together with hydrazine can form hydrazinium carbazate salt that can jam valves or block injector orifices . NOTE 2 NH3 in N2H4 can degrade the catalyst performance of hydrazine thrusters , especially for cold starts . NOTE 3 N2 in LOx can lower the performance of the propulsion system as compared to non - contaminated LOx .