A ventilation system includes a housing having an inlet and an outlet to facilitate air flow, a fan coupled within the housing, a filter removably coupled within the housing and a litter box coupled to the housing. In implementations the ventilation system defines a flow direction for air exiting the litter box and the fan is positioned prior to the filter in the flow direction. In implementations an adhesive element having an opening is coupled to the bottom of the housing and the opening is aligned with the inlet, and a transparent coupler is coupled to the adhesive element, the transparent coupler blocking at least one vent of the litter box and the transparent coupler having an opening aligned with the inlet. In implementations the ventilation system defines substantially only a single flow direction for the air flow, the flow direction being in an upwards direction from the litter box.
