Gas borne particle filtering method

In a method of filtering gas borne particles in a filtering apparatus wherein inlet and outlet openings (11 and 12) in the apparatus are separated by a filter medium (13) mounted on a porous support (14) for filtration, the improvement which comprises:

• (a) providing a small mesh screen as the porous support (14) composed of polymeric strands, the screen having a mesh size of about 6 or greater, in contact with the filter medium (13) which is non-metallic and has a density of about 3.2.times.10.sup.-3 to 6.28.times.10.sup.-1 grams per cubic centimeter wherein upon interaction of the screen in contact with the filter medium during gas flow across an exposed surface of the filter medium opposite the contact with the screen by a fluttering movement of the filter medium on the screen an electrostatic charge is created which attracts 0.1 micron and larger sized particles to the filter medium for removal from the gas;
• and
• (b) flowing a gas along the surface of the filter medium, through the filter medium and then the screen at a gas velocity of between about 25 and 1000 feet per minute at a pressure drop across the filter medium of less than about 2 inches of water, wherein an increasing percentage of the particles of a particular size are removed as a result of particle loading of the filter medium during filtration.