Every occupant of a dwelling containing a single dwelling unit shall be responsible for the extermination of any insects, rodents or other pests therein or on the premises, and every occupant of a dwelling unit in a dwelling containing more than one dwelling unit shall be responsible for such extermination whenever his dwelling unit is the only one infested. Notwithstanding the foregoing provisions of this subsection, whenever infestation is caused by failure of the owner to maintain a dwelling in a ratproof and insectproof condition, extermination shall be the responsibility of the owner. Whenever infestation exists in two or more dwelling units in any dwelling, or in the shared or public parts of any dwelling containing two or more of the dwelling units in any dwelling, or in the shared or public parts of any dwelling containing two or more dwelling units, extermination thereof shall be the responsibility of the owner. (Prior code § 11-29)