2703.10.4 Exhaust Ducts for HPM
An approved automatic sprinkler system shall be provided in metallic and noncombustible nonmetallic exhaust ducts where all of the following conditions apply:
- Where the largest cross-sectional diameter is equal to or greater than 10 inches (254 mm).
- The ducts are within the building.
- The ducts are conveying flammable gases, vapors or fumes.
An approved automatic sprinkler system shall be provided in combustible nonmetallic exhaust ducts where the largest cross-sectional diameter of the duct is equal to or greater than 10 inches (254 mm).
- Ducts listed or approved for applications without automatic sprinkler system protection.
- Ducts not more than 12 feet (3658 mm) in length installed below ceiling level.