The mechanical draft system vent shall vertically terminate at least how many feet below window or gravity air inlet for the building?

The correct answer is that the mechanical draft system vent must vertically terminate at least 4 feet below a window or gravity air inlet for the building. This requirement is designed to prevent any potential backdraft or exhaust gases from entering the living space, which can occur if the vent is positioned too close to openings in the building. By maintaining a minimum separation distance, it ensures that harmful gases and particulates from the exhaust are safely directed away from areas where they could pose a health risk to occupants.

Maintaining this distance is crucial for ensuring proper ventilation and indoor air quality, as well as complying with codes and regulations that govern HVAC systems. The code is often established based on industry standards to mitigate risks of carbon monoxide poisoning and other hazards associated with improperly vented systems.