How many inches must the exit terminal of a mechanical draft system be above the anticipated slow line?

The exit terminal of a mechanical draft system must be positioned at least 12 inches above the anticipated slow line to ensure proper ventilation and effective operation. This requirement is crucial for preventing the backflow of exhaust gases into the system, which could lead to safety hazards such as carbon monoxide buildup.

Positioning the terminal at this height helps to accommodate natural airflow and protect against potential obstructions, such as snow or debris, that could impede the exhaust flow. By adhering to the 12-inch guideline, the system can function efficiently, maintaining adequate draft and minimizing the risk of downdrafts that could disrupt proper venting. This is a standard practice in maintaining safety and functionality in gas appliances and mechanical systems.