[en] Gaseous effluents containing nitrogen oxides and radioactive additions are first cleaned of dust and aerosols in aqueous solutions of nitric acid. They are then absorbed in an aqueous solution or a suspension of ammonium salts of polybasic acids with a dissociation constant of the order of 10^-4 to 10^-7 at a temperature of 50 to 80 degC. The ¹⁰⁶RuO₄ present in the effluent is absorbed in a solution of an alkali permanganate and/or manganate at pH 10 to 14 and/or at pH 8 to 9 in a water suspension of hydrated MnO₂. The resulting effluent still containing some ¹⁰⁶RuO₄ and NO traces is absorbed in an alkali hydroxide aqueous solution in the presence of zinc and/or aluminium metal. (J.P.)