Abstract: A multiple stage filter assembly which combines a permanently framed particulate filter media layer with an odor and particulate removal filter media layer which is removably mounted to the particulate permanent filter frame in overlying relationship to the outer surface of the particulate layer. The odor removal filter media layer is held in position by a plurality of filter retaining members which cooperate with the main frame structure to provide support for the gaseous filter layer. The retaining members function in a manner which permits simple removal and replacement of the gaseous filter layer without disturbing the permanently framed particulate filter layer.

Abstract: An improved filter construction for odor adsorption adapted to fit into a frame provided with front and rear support faces. The filter media consists of one or more sheets of non-woven material impregnated with activated carbon particles. Each sheet is provided with a plurality of slit and expanded openings to permit gaseous flow through said sheet. The sheet material comprises a combination of cellulose and synthetic fibers in a weight percentage range of between at least 30 to 50 percent of cellulose fibers and 1 to 10 percent of synthetic fibers wherin the combination of the two fibers represent at least 40 percent of the total composition of the sheet. The activated carbon content is between 35 to 50 percent of the total composition by weight. A latex binder material and a wet strength resin are included for fabrication of the sheet and to reduce dusting of the charcoal.