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NOTE: When the exhaust ductwork passes through a wall, ceiling, or roof made of combustible
materials, the opening must be 2-inches (5.08 cm) larger than the duct (all the way around).
The duct must be centered within this opening.
Outside Ductwork Protection
To protect the outside end of the horizontal ductwork from the weather, a 90° elbow bent downward should be
installed where the exhaust exits the building. If the ductwork travels vertically up through the roof, it should be
protected from the weather by using a 180° turn to point the opening downward. In either case, allow at least
twice the diameter of the duct between the duct opening and the nearest obstruction.
IMPORTANT: DO NOT use screens, louvers, or caps on the outside opening of the exhaust
ductwork.