The lowest portion of the floor furnace shall have not less than a ________ - inch clearance from grade level.

For a floor furnace, maintaining a clearance from grade level is essential for safety and effective operation. A clearance of 6 inches from the grade level is required to ensure adequate airflow to the furnace, minimizing the risk of obstruction from snow, debris, or other materials that could potentially block the air intake. This distance is also critical for preventing any potential hazards associated with overheating and ensuring that the furnace can perform efficiently without risk of contamination or damage. By adhering to this clearance requirement, one helps guarantee proper functioning and safety of the heating system.