PENETRATION OF TEST AEROSOLS THROUGH FILTERS DESCRIBED IN TERMS OF A GAMMA-DISTRIBUTION OF LAYER EFFICIENCIES

Filters have been tested with standard and modified standard aerosols. The tests have been carried out on several filter materials, and on a range of thicknesses of each. The results are expressed in the form of penetration/pressure drop plots. If it is assumed that the layer efficiency of the filters against these polydisperse aerosols takes the form of a Gamma distribution, the penetration can be described by a simple two-parameter function of the thickness, area weight or pressure drop. Curve fitting techniques have been used to fit such functions to experimental data, and the fits have been shown to be satisfactory for filters with a wide range of efficiencies. The quality of fit implies that the design of a filter to meet a specific requirement could be made reasonably well on the basis of at least two accurate measurements.