Applicable codes and standards provide requirements for exhaust ducts connected to Type I (grease and smoke emitting) exhaust hoods. For many years, legacy and existing duct products have been predominantly 16-gauge carbon steel and mostly rectangular in shape. These ducts are usually planned, measured, fitted, and welded on-site, to comply with applicable codes and standards for materials, welding, connections, slope, drains, cleaning access, and other provisions.
Despite the good intentions of fabricators and installers, visits to operating foodservice facilities and fire scenes suggest there are challenges with unlisted, welded-on-site ducts, including: