Adsorption of NO, NO2 and NO + NO2 was studied with and without O2 in the gas feed on NaY zeolite (Si/Al = 2.55) at 30 °C and 101.3 kPa. The influence of residual water in NaY was also studied in presence of O2 in the gaseous flux. During adsorption of NO, NO2 is produced in presence of O2 in the gas feed, due to the formation of oxygen species at the surface of the zeolite. Then, created NO2 reacts with residual H2O to form NO. Without O2, the production of NO2 does not occur. If residual H2O is removed, reaction of NO2 with H2O leading to the formation of NO does not happen. Whether with or without O2 in the gas feed during NO2 adsorption, the evolution of NO and NO2 outlet concentrations are similar. First, NO2 is adsorbed, producing NO by reacting with residual H2O and then, the production of NO decreases while NO2 outlet concentration increases. NO2 breakthrough time is slightly higher without O2. In absence of residual water, no NO is produced. Concerning adsorption of NO and NO2 mixture, the evolution of outlet concentrations is different in presence or in absence of O2. With O2, final outlet concentrations of NO and NO2 are not equal to inlet concentrations unlike what happens without O2. With a dried NaY sample, NO2 is adsorbed without forming NO. For all experiments performed, NO is not adsorbed whereas NaY is interesting for NO2 adsorption, even in gaseous mixture adsorption. [ABSTRACT FROM AUTHOR]