D.C. Mun. Regs. tit. 14 § 400
No owner, licensee, or tenant shall occupy or permit the occupancy of any habitation in violation of this subtitle.
Every owner or licensee shall advise each tenant in writing, either by insertion in the lease between the parties or otherwise, of the maximum number of occupants permitted under this subtitle in the habitation leased or rented to that tenant.
No person shall rent or offer to rent any habitation, or the furnishings of a habitation, unless the habitation and its furnishings are in a clean, safe, and sanitary condition, in repair, and free from rodents or vermin.
The owner or licensee of each residential building shall provide and maintain the facilities, utilities, and services required by this subtitle.
Each facility and utility provided in a residential building to comply with the requirements of this subtitle shall be properly and safely installed, and shall be maintained in a safe and good working condition.
If an owner or licensee of any residential building furnishes any facilities for cooking, storage, or refrigeration of food, those facilities shall be maintained by the owner or licensee in a safe and good working condition.
No person shall rent or offer for rent any habitation or operate any housing business in any building, or part of a building, in which there is another business, trade, or commercial activity from which noxious gases, fumes, mists, vapors, dusts, offensive odors, or excessive noise arise or are generated.
The use of any building or other structure (or any part of any building or structure) as a tenement unit or tenement house is prohibited.
D.C. Mun. Regs. Tit. 14, § 400