Final answer:
The upper edge of a masonry chimney cleanout should be at least eight inches below the lowest inlet opening to ensure safe and efficient operation, especially when using a wood stove or similar device.
Step-by-step explanation:
The upper edge of a masonry chimney cleanout should be at least eight inches below the lowest inlet opening. This is necessary to ensure that the chimney operates safely and efficiently, particularly if connected to a wood stove or other efficient device, which prevents most heat from escaping through the chimney. The correct distance helps in maintaining a proper draft, preventing backflow of gases, and allowing for easier cleaning and maintenance of the chimney.