Patent ID: 7398887

Claim:
A multi-layer filter media comprising a combination of at least two successive adjacent face-to-face thicknesses of selected filter fiber sizes with each thickness having fiber sizes so that the pore size characteristics of one thickness differs from that of an adjacent thickness with said fibers of one thickness being comparatively finer than said fibers of said other thickness and with the fiber sizes and pore sizes of said successive adjacent face-to-face thicknesses of fibers being calculated with an arrangement so that the overall average pore size of the combined successive thicknesses is smaller than that of the average overall pore size of that of the finest fiber thickness, whereby the average pore size of an “n” layered media is defined by the formula: 1 M = ɛ i ⁢ ɛ i + 1 ⁢ ⁢ … ⁢ ⁢ ɛ n ( ∑ i = 1 n ⁢ 1 M i ) wherein the porosity of “ε” is the ratio of the pore volume to the total volume of medium, “Σ” is the summation from i=1 to n, and “M” is the mean flow pore diameter of the filter media layers, said multi-layer filter media having an equal share of terminal differential pressure on each of said at least two successive adjacent face-to-face thicknesses, thereby maximizing holding capacity for a predefined fluid stream.