Multi-phase filter medium

An article, comprising:

• a first phase comprising a first plurality of fibers and a second plurality of fibers different from the first plurality of fibers;
• a second phase comprising a third plurality of fibers and a fourth plurality of fibers different from the third plurality of fibers, the third plurality of fibers being the same as or different from the first or second plurality of fibers and the fourth plurality of fibers being the same as or different from the first or second plurality of fibers;
• a transition phase between the first and second phases, wherein the transition phase comprises at least a portion of the first plurality of fibers, at least a portion of the second plurality of fibers, at least a portion of the third plurality of fibers, and at least a portion of the fourth plurality of fibers, and wherein at least a portion of the first plurality of fibers, at least a portion of the second plurality of fibers, at least a portion of the third plurality of fibers, and at least a portion of the fourth plurality of fibers are intermingled with each other,
• wherein the air permeability of the first plurality of fibers is higher than the air permeability of the second plurality of fibers, the air permeability of the third plurality of fibers is higher than the air permeability of the fourth plurality of fibers, and at least one of the first, second, third, and fourth pluralities of fibers are made from an organic polymeric material,
• wherein the basis weight ratio of the first phase to the second phase is from about 30:70 to about 70:30, and
• wherein the article is configured as a filter medium.