Method of filtering particulates from the air using a composite filter substrate comprising a mixture of fibers

A method of filtering particulates from the air comprising the steps of:

• a. providing an air filtering device in a room, wherein said device comprises
• a fan;
• and
• an air filter bag having an open end to receive air from said fan, the air filter bag comprising:
• a first component layer comprising:
• a mixture of fibers comprising shaped fibers having at least two different deniers, wherein each fiber in said mixture comprises a denier from about 0.7 dpf to about 7.0 dpf;
• a plurality of hollow protrusions and recessed regions, wherein said hollow protrusions comprise a protruded length from about 3 mm to about 16 mm and a non-protruded length from about 2 mm to about 14 mm and a protruded height from about 0.5 mm to about 3 mm, and wherein said hollow protrusions and recessed regions comprise a planar area ratio from about 40:60 to about 60:40;
• and
• a second component layer comprising at least about 50% of fibers having a denier from about 0.9 dpf to about 2.0;
• a third component layer, wherein the second component layer is disposed between the first and third component layers;
• a plurality of connections connecting said first component layer and said second component layer, wherein the plurality of connections comprise mechanical interpenetration of fibers, wherein said air filter bag has a thickness from about 1 mm and about 3 mm and a basis weight from about 30 gsm to about 100 gsm;
• and
• b. activating said fan to move about 70 to about 150 CFM of air to said air filter bag with an air pressure drop through said air filter bag of about 4 Pa to about 25 Pa.