Abstract: A filter assembly is used in a return air grille of an HVAC system to filter dust, particles and contaminants from air. The filter assembly includes a filter cartridge having a frame that surrounds an air filter. The frame includes a planar surface that defines a plane. The filter cartridge and the frame flange are separate components. A frame flange is attached only to the planar surface of the frame.

Abstract: A system for circulating air which includes particles, bacterial organisms, and odoriferous material includes a fan coupled to ducting of the air circulation system for causing movement of air in a stream through the ducting; a filter holder configured to hold an air filtering device supported within the air stream; and an air filtering device for removing from the circulating air the particles, bacterial organisms, and odoriferous material. The air filtering device may include multiple filter elements having multiple layers of differing filtering materials, which may include activated carbon and potassium permanganate.

Abstract: A filter media for an air filter includes at least two layers of filter material with the materials being different. The layers are joined together by a stiffening grid fabricated from a metal or plastic. Glue such as hot-melt glue is disposed on both sides of the grid to attach the sides of the grid to the respective layers. Depending upon the application, the filter media may be pleated.