This work is part of the EDF project "control of α-particle radiation risk in nuclear power stations". A realistic determination of the resuspension factor of contamination is necessary to be certain that the health protection measures taken by the EDF for their on-site workers are applicable. An experimental determination of the resuspension factor during the programmed maintenance of Unit 3 of the Cattenom power station, which suffered a dispersion of fissile material during a stoppage in January 2001, has been performed. The values of the surface and atmospheric activity concentrations at three workspace (pressure unit, steam generator and pool of the reactor building) are analysed. The results allow setting the most realistic value of the resuspension factor for α-particle for operational radiation protection at F MES=1×-6 m-1. © 2004 EDP Sciences.