308.3.4 Clearance from supply ducts.
FGC § 308.3.4
Supply air ducts connecting to listed central heating furnaces shall have the same minimum clearance to combustibles as required for the furnace supply plenum for a distance of not less than 3 feet (914.4 mm) from the supply plenum. Clearance is not required beyond the 3-foot (914.4 mm) distance.













