Common Duct is defined as which of the following?

• A. The duct work containing the exhaust air from two or more branch ducts.
• B. The duct work that channels exhaust from one appliance.
• C. The duct work used for intake air only.
• D. The duct work containing the exhaust air from a single hood.

Answer: (B)

The main idea here is understanding what the term common duct refers to in kitchen ventilation. In this context, the common duct is the duct work that channels exhaust from one appliance. It serves as the dedicated path for the grease-laden exhaust from that single hood or appliance to the outside. This path must be sized for the appliance’s exhaust, built to handle grease and heat, and provide access for cleaning and inspection, with appropriate fire protection as required by code. The other phrasing would describe ducts that handle intake air or ducts that collect exhaust from multiple hoods, which are different arrangements.