Composite filter media with multiple fiber structures including nanofibers

A filter media for use in a filter element, comprising:

• a first fiber layer;
• a second fiber layer positioned downstream of the first fiber layer, the first fiber layer having a first geometric mean fiber diameter of less than 1 μm, a first geometric standard deviation of fiber diameter greater than 2.0, and a first pore size distribution corresponding to a first P99/P50 ratio, the first P99/P50 ratio based on a first mean flow pore size P50 of less than 3 μm, and the second fiber layer having a second geometric mean fiber diameter of less than 1 μm, a second geometric standard deviation of fiber diameter less than or equal to 2.0, and a second pore size distribution corresponding to a second P99/P50 ratio, the second P99/P50 ratio based on a second mean flow pore size P50 of less than 10 μm, wherein the second P99/P50 ratio is less than the first P99/P50 ratio, wherein the first P99/P50 ratio is greater than 3 and the second P99/P50 ratio is less than 2, wherein the first fiber layer comprises nanofibers in a first amount and microfibers in a second amount that is less than the first amount, and wherein a ratio of a first Frazier permeability of the first fiber layer to a second Frazier permeability of the second fiber layer is within a range of 0.3 and 2.0, inclusive;
• and
• a substrate positioned downstream of the second fiber layer such that the second fiber layer is disposed between the first fiber layer and the substrate, the substrate comprising coarser fibers than each of the first fiber layer and the second fiber layer and having a third geometric mean fiber diameter of larger than 1 μm.