Nanofiber filter, with fibers 98-300 nm, has been used to effectively remove sub-micron aerosol. Despite the effectiveness of filtration, the pressure drop of the filter is high and increases with solid aerosol loading. In this study, the pressure drop and filtration efficiency of nanofiber filter were investigated experimentally. In particular, the empirical model of Brown was modified to determine the distribution of aerosol deposit across filter thickness using the experimental parameters. It was found that there is a large pressure drop across the loaded thin nanofiber layer, and likewise aerosol deposit distributed largely non-uniformly across the filter thickness, with more aerosol deposited near the face region compared to the back side. This can be regarded as the skin effect that exists particularly in nanofiber filtration of sub-micron aerosol. This skin effect can be mitigated by installing a microfiber filter upstream of the nanofiber filter. This is confirmed by a lower measured pressure drop across the inhomogeneous dual-layer filter. (C) 2011 Elsevier B.V. All rights reserved.