Installing a secondary decomposing catalyst is an effective method for nitrous oxide emission reduction at a nitric acid production facility. Before the installation of a decomposing catalyst at a nitric acid plant in Devnya, Bulgaria, the N₂O concentration in the tail gas was 1,754 mg/Nm³ while after the installation the N₂O concentration was 212 mg/Nm³, which is almost 8.3 times lower. For the entire monitoring period a total N₂O emission reduction of 7,021 Mg was achieved. Research of the catalyst’s behavior during the production campaign has been done, proving that the achieved reduction level depends on the catalyst’s functional activity and the technological process conditions. Planning the duration of the decomposing catalyst’s efficient operation throughout N₂O monitoring data analysis provides effective emission reduction.