Experiments are carried out using special filters with known structural characteristics to study the stationary phase of filtration of liquid aerosols by fibrous filters in the diffusion, interception and inertial regimes. In the domains of diffusion and interception, a comparison made with published models has enabled the selection of two relationships correctly describing these mechanisms both in the slip and continuum regimes. On the other hand, in the inertial domain, an empirical correlation has been established for the single fiber impaction efficiency for viscous flows. All our results have been validated by measurements on an industrial filter.