An odor filter apparatus for a litter box, the odor filter apparatus comprising: a vent base, with a top side and a bottom side； an inlet opening in the vent base； a plurality of channels in the bottom side of the vent base, configured to direct air flow to the inlet opening； a filter housing attached to the top side of the vent base； an active odor removing element located in the filter housing； a fan assembly housing removeably attached to the filter housing； a blower fan located in the fan assembly housing； a mounting opening in the fan assembly opening； a fan exhaust sealing device attached to the mounting opening； four soft button feet attached to the bottom side of the vent base； wherein the blower fan is configured to pull air through the inlet opening, through the active odor removing element, and out through the fan exhaust sealing device. An odor filter apparatus for a litter box, the odor filter apparatus comprising: a litter box bottom； a litter box top configured to sit on the litter box bottom； a vent in the litter box top； a filter housing attached to the litter box top； an active odor removing element located in the filter housing； a fan assembly housing removeably attached to the filter housing； a blower fan located in the fan assembly housing； a mounting opening in the fan assembly opening； a fan exhaust sealing device attached to the mounting opening； wherein the blower fan is configured to pull air through the vent, through the active odor removing element, and out through the fan exhaust sealing device. An odor filter apparatus for a litter box, the odor filter apparatus comprising: a rear wall, the rear wall configured to rigidly attach to a litter box bottom； a first side wall located on one side of the rear wall, and orientated orthogonally to the rear wall, the first side wall configured to rigidly attach to a litter box bottom； a second side wall located on an opposite side of the rear wall from the first side wall, and orientated orthogona
