D.C. Mun. Regs. tit. 14 § 501
Adequate heating facilities shall mean the provision and maintenance in good repair of one of the following:
The heating facility shall be capable of maintaining a minimum temperature of seventy degrees Fahrenheit (70° F.) in buildings or parts of buildings used for habitation.
Each heating facility shall be designed and installed to permit the control of the temperature resulting from the use of that facility in such manner that the maximum resulting temperature in the premises heated by such facility will not exceed the maximum temperature in the "Comfort Chart" contained in the 1951 Guide of the American Society of Heating and Ventilating Engineers.
Whenever the heating facilities of any habitation or bathroom are not under control of an occupant of the habitation, it shall be the responsibility of the owner or licensee to supply sufficient heat to maintain the following minimum temperatures for every occupied habitation and bathroom:
The temperatures referred to in this section shall be measured with all usually- closed outside openings closed in a normal manner.
The owner of a single-family dwelling, occupied in whole or in part by a tenant or tenants in which one (1) or more housing violation notices were issued because of a defective heating system under the control of the owner, shall cause the furnace, boiler, or other central heating or hot water system to be inspected by a qualified person in the period between March 1st and September 1st subsequent to the issuance of the violation notices.
In addition to testing the efficiency and adequacy of the heating and hot water systems, the flues, vents, and dampers shall be inspected for escape of carbon monoxide gas.
The findings on inspections shall be recorded on forms approved by the Department of Consumer and Regulatory Affairs ("Department") within fifteen (15) days following the inspection and shall be delivered to the owner, who shall file a copy with the Department within seven (7) days of the receipt of the findings.
The owner shall correct all defects as found upon the inspection before October 1st of that year and shall certify to the Department that the corrections have been made.
The owner of a multiple dwelling, containing two (2) or more units, shall cause the furnace, boiler, or other central heating systems to be inspected by a qualified person between March 1st and September 1st of each year. Subsections 501.7 through 501.9 shall also apply to this subsection.
For purposes of §§ 501.6 through 501.10, the term "qualified person" means a master plumber and gas fitter, heating and air conditioning contractor, master mechanic, licensed by the District, or a certified employee of a public utility.
The certifications required by §§ 501.6 through 501.10 shall be in writing and shall be signed by the owner and by a "qualified person."
D.C. Mun. Regs. Tit. 14, § 501