We present a simple model for the loading process of aerosol particles on fibrous filters with the aim to show the influence that the flow recalculation around a single fibre has on the complete loading process, up to the final clogging of the filter. At each loading stage (i.e., at any given degree of particle deposition), the change of shape of the fibre is presented, and information on the flow field around a fibre and the filter efficiency are obtained. The effect of the flow recalculation on the filter efficiency is shown; the single fibre efficiency is proven to be overestimated when the effect of further deposition is neglected. To perform the study, we have developed a CFD code and we have combined it with particle trajectory simulations. (C) 2003 Elsevier B.V. All rights reserved.