D.C. Mun. Regs. tit. 12, r. 12-B1503
Strike Section M1503.1 of the International Residential Code in its entirety and insert a new Section M1503.1 into the Residential Code in its place to read as follows:
General. Range hoods or down-draft exhaust systems shall be required above ranges and cooktops. Range hoods and down-draft exhaust systems shall discharge to the outdoors through a duct. The duct serving the hood shall have a smooth interior surface, shall be airtight, shall be equipped with a back-draft damper and shall be independent of all other exhaust systems. Ducts serving range hoods or down-draft exhaust systems shall not terminate in an attic or crawl space or areas inside the building.
Exception: Where a minimum 100 cfm intermittent kitchen exhaust mechanical system is otherwise provided in accordance with Section M1507.4, listed and labeled ductless range hoods installed in accordance with the manufacturer's instructions shall not be required to discharge to the outdoors.
D.C. Mun. Regs. tit. 12, r. 12-B1503