304.11 Combustion air ducts.
FGC § 304.11
Combustion air ducts shall comply with all of the following: 1. Be of galvanized steel complying with Chapter 6 of the New York City Mechanical Code or of equivalent corrosion-resistant material approved for this application. Exception: Within dwelling units, unobstructed stud and joist spaces shall not be prohibited from conveying combustion air, provided that not more than one required fireblock is removed.
2.Have a minimum dimension of 3 inches (76.2 mm) in all directions.
3.Terminate in an unobstructed space allowing free movement of combustion air to the appliances.
4.Have the same cross-sectional areas as the free area of the openings to which they connect.
5.Serve a single appliance enclosure.
6.Not serve both upper and lower combustion air openings where both such openings are used. The separation between ducts serving upper and lower combustion air openings shall be maintained to the source of combustion air.
7.Not be screened where terminating in an attic space.
8.Not slope downward toward the source of combustion air, where serving the upper required combustion air opening.
9.Be constructed so that the remaining space surrounding a chimney or chimney liner, installed within a masonry, metal or factory-built chimney cannot be used to supply combustion, ventilation and dilution air, except for direct vent appliances designed and installed in accordance with the equipment manufacturer's instructions and listing.
