Intercomparison experiments between a widely used Russian (＇＇IBP＇＇) aerosol impactor (Institute of Biophysics, Moscow) and several western standard aerosol measuring devices have been performed, including Berner Impactor, Monodisperse Aerosol Generator, Aerodynamic Particle Sizer and Differential Mobility Analyser. Comparisons of the previously used cut-off diameters determined by Shuravel (1993, Ukrainian Academy of Science, Kharkov) with impaction theory (Marple (1970) Ph.D. thesis, University of Minnesota) show deviations, especially for the smaller particle ranges. Laboratory and field experiments have been performed to determine a correction formula. This correction can be expressed by an exponential function of the particle diameter. The results are applied to examples of earlier measurements in the cabins of tractors working in the regions contaminated after the Chernobyl accident.