Filtration Article with Heat-Treated and Shrunken Fluoropolymer Knit

A filtration article for filtering particles from a fluid stream, comprising:

• a first layer, positionable across said fluid stream, comprising a porous PTFE membrane for filtering particles from said fluid stream;
• and
• a second layer, positionable across said fluid stream to provide for at least one of drainage of and support of said first layer, comprising a plurality of strands of fluoropolymer fibers arranged to form a knit having a plurality of interlocking regions that are each defined by corresponding different sets of at least two interlocking loop portions of said plurality of strands of fluoropolymer fibers, wherein said plurality of interlocking regions of the knit define a plurality of wales and a plurality of courses, and wherein for at least a first portion of said plurality of strands each strand comprises different loop portions that partially define different, alternating ones of said plurality of interlocking regions located along at least two different ones of said plurality of wales;
• wherein said second layer has an aperture area of less than about 0.08 mm2.