D.C. Mun. Regs. tit. 14 § 805
The occupant of any single-family dwelling shall keep the premises free from vermin, rodents, and rodent harborage.
The occupant of any habitation in a two-family or multiple dwelling shall be responsible for the extermination of vermin and rodents whenever his or her habitation is the only one infested, except as provided otherwise in § 805.3.
If an infestation of a single habitation is caused by failure of the owner or licensee to maintain a residential building in a rodent-proof or reasonably insect-proof condition, the exterminating shall be done by the owner or licensee.
The owner or licensee of a two-family or multiple dwelling shall keep the common space in that residential building free from vermin and rodents, and rodent harborages.
The extermination of vermin and rodents shall be done by the owner or licensee whenever infestation exists in two (2) or more of the habitations in two-family or multiple dwellings.
D.C. Mun. Regs. Tit. 14, § 805