GE CV966 Owner's Manual And Installation Instructions page 10

Installation Instructions
This Hood Must Use 7" Round Duct.
It Can Transition To 3-1/4" x 12" Duct.
Note: Any home ventilation system, such as a ventilation
hood, may interrupt the proper flow of combustion air and
heaters and other naturally vented systems. To minimize the
chance of interruption of such naturally vented systems, follow
the heating equipment manufacturer's guidelines and safety
standards such as those published by NFPA and ASHRAE.
When applicable, install any makeup (replacement) air system
in accordance with local building code requirements. Visit
GEAppliances.com for available makeup air solutions.
Using a smaller diameter duct size
will reduce performance.
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