A chimney for a residential low heat utilization equipment shall extend at least how many feet?

• A. 6 inches
• B. 3 feet
• C. 2 feet
• D. 1 foot

Answer: (B)

Extending the chimney enough to establish a reliable upward draft is essential for safe venting. For residential low-heat equipment, the vent must extend at least three feet above the highest point where it passes through the roof (and above any part of the building within ten feet) to minimize downdrafts and backflow of combustion gases. Shorter extensions—such as six inches, one foot, or two feet—can be more easily affected by wind and nearby structures, increasing the risk of exhaust gases re-entering the living space or not venting properly. So the minimum required extension is three feet.