[en] A method for determining ¹²⁹I in atmospheric air is presented. It consists of the following stages: sampling (of aerosol and gas fraction separately), preparation of a sample for irradiation in a reactor by a destructive distillation method, irradiation of samples in a reactor, radiochemical separation and ¹³⁰I activity measurements by slow coincides. Iodine isotopes (including ¹²⁹I) in the atmospheric air have mostly been found in gas fractions (except ¹³²I). Gas compounds and percentages of radioactive and stable iodine isotopes coincide. (author) 7 refs.; 1 fig.; 1 tab