Fibrous filter media

A composite, glass fiber air filtration media comprising:

• a foraminous backing layer for reinforcing the composite air filtration media forming a downstream layer of said composite air filtration media;
• an intermediate layer of fine glass fibers for collecting fine particles from an air stream bonded to said foraminous backing layer;
• said fine glass fibers having an average fiber diameter ranging from about 2.5.times.10.sup.-5 to about 6.0.times.10.sup.-5 inches;
• said intermediate layer of fine glass fibers weighing between 1.1 and 2.7 grams per square foot;
• and the thickness of said foraminous backing layer and said intermediate layer of fine glass fibers ranging from about 0.10 to about 0.15 inches;
• and
• an upstream layer of coarse glass fibers for collecting coarse particles from an air stream;
• said upstream layer of coarse glass fibers being bonded to said intermediate layer of fine glass fibers;
• said coarse glass fibers having average fiber diameters ranging from about 8.0.times.10.sup.-5 to about 18.0.times.10.sup.-5 inches;
• said upstream layer of coarse glass fibers weighing between 2.1 and 4.1 grams per square foot;
• and the thickness of said foraminous backing layer, said intermediate layer of fine glass fibers and said upstream layer of said coarse glass fibers ranging from about 0.20 to about 0.32 inches.