How far below any gravity openings must mechanical draft systems be installed?

Mechanical draft systems must be installed at least 3 feet below any gravity openings such as windows, doors, and other vents. This requirement is crucial to ensure that the mechanical draft does not interfere with the natural flow of air from gravity openings, which could lead to unsafe conditions.

Having the mechanical draft system installed 3 feet below these openings helps prevent potential backdrafting of combustion gases, improving safety by ensuring that harmful emissions do not enter the building. Additionally, this distance aids in guaranteeing proper ventilation and maintaining the effectiveness of both mechanical and natural draft systems, promoting overall air quality and safety within the structure.

The other distances provided do not meet the established safety guidelines and would not adequately ensure the effective operation of the mechanical draft system in relation to gravity openings.