The air duct for combustion must be located how far from the ceiling and floor respectively?

The air duct for combustion must be located how far from the ceiling and floor respectively?

• A. 12 inches from the ceiling and 12 inches from the floor
• B. 6 inches from the ceiling and 6 inches from the floor
• C. 24 inches from the ceiling and 12 inches from the floor
• D. 12 inches from the ceiling and 24 inches from the floor

Answer: (A)

Combustion air should be drawn from a mid‑height portion of the space so the air is fairly well mixed and not strongly affected by hot air near the ceiling or cold air near the floor. The code specifies that the combustion air duct openings be located 12 inches from the ceiling and 12 inches from the floor. This placement keeps the intake in a stable, middle zone, reducing the potential for drafts, stratification, or drawing in air that could upset combustion or introduce combustion products into the living space.

Combustion air should be drawn from a mid‑height portion of the space so the air is fairly well mixed and not strongly affected by hot air near the ceiling or cold air near the floor. The code specifies that the combustion air duct openings be located 12 inches from the ceiling and 12 inches from the floor. This placement keeps the intake in a stable, middle zone, reducing the potential for drafts, stratification, or drawing in air that could upset combustion or introduce combustion products into the living space.