D.C. Mun. Regs. tit. 25, r. 25-B1810
All rooms shall have sufficient tempered make-up air and exhaust ventilation to keep them free of excessive heat, steam, condensation, vapors, obnoxious odors, smoke, and fumes.
All ventilation systems, furnaces, gas- or oil-fired room heaters, and water heaters shall be designed, installed, and operated in accordance with the Plumbing Code.
Each room in which food or drink is prepared, or in which utensils are washed, shall be provided with facilities for at least eight (8) air changes per hour. Recirculation of air is not permitted.
Each food processing operation that creates smoke, steam, gases, fumes, odors, vapors, or excessive heat shall be hooded and vented, or locally vented to the outside air by forced draft, in a manner that will effectively remove the conditions.
D.C. Mun. Regs. tit. 25, r. 25-B1810