Penetration of aerosol particles through fine fibrous filters

Abstract

The penetration of submicron particles through fine-fibrous filtering materials is studied. The existing theoretical approach to the description of the fine filtration of aerosols on the basis of the fan model filter is compared with experiments performed on a TSI 31–60 unit. Monodisperse aerosols of sodium chloride and dioctylphthalate are passed through several layers of filtering materials consisting of ultrafine polydisperse fibers. From measurements, it follows that the logarithm of the penetration coefficient of particles with radius r = 0.05–0.20 μm is directly proportional to the number of layers. The most penetrating particle radii r* found from experiments within this range of r and the collection coefficients corresponding to them are in good agreement with the calculations performed for the model on fan filter in the mode of diffusion deposition of finite-size particles with consideration for the slip of a gas over fibers, the action of retarded van der Waals forces, and also the polydispersity of fibers and the structural heterogeneity of filters. The penetrations measured for particles with r < 0.04 μm do not correspond to the exponential law of filtration. The penetration is increased in each subsequent layer of material.