Ducts shall be constructed of not less than which gauges for carbon steel and stainless steel?

Ducts shall be constructed of not less than which gauges for carbon steel and stainless steel?

• A. 16 and 18
• B. 14 and 16
• C. 18 and 20
• D. 16 and 18 (correct)

Answer: (D)

The concept being tested is how duct material thickness is chosen to maintain structural integrity and cleanliness in a grease-heavy kitchen exhaust environment. In NFPA 96, carbon steel ducts must be made from a relatively thicker sheet metal, while stainless steel ducts can use a slightly thinner sheet metal without compromising strength or hygiene. This distinction exists because carbon steel is more prone to corrosion and denting if the metal is too thin, so a thicker thickness is required to withstand cleaning, grease exposure, heat, and ductwork loading. Stainless steel, on the other hand, offers superior corrosion resistance and easier cleaning, allowing for the necessary strength at a thinner gauge while still meeting safety and fire-protection goals. The result is a practical balance of durability, maintenance, and cost.

The concept being tested is how duct material thickness is chosen to maintain structural integrity and cleanliness in a grease-heavy kitchen exhaust environment. In NFPA 96, carbon steel ducts must be made from a relatively thicker sheet metal, while stainless steel ducts can use a slightly thinner sheet metal without compromising strength or hygiene. This distinction exists because carbon steel is more prone to corrosion and denting if the metal is too thin, so a thicker thickness is required to withstand cleaning, grease exposure, heat, and ductwork loading. Stainless steel, on the other hand, offers superior corrosion resistance and easier cleaning, allowing for the necessary strength at a thinner gauge while still meeting safety and fire-protection goals. The result is a practical balance of durability, maintenance, and cost.