In a confined space, the upper opening for combustion air must be within 12 inches of the ceiling.

• A. Yes
• B. No
• C. Only for certain appliances
• D. Not specified

Answer: (A)

When a fuel-burning appliance is in a confined space, you need a reliable flow of fresh air from both high and low openings to prevent dangerous negative pressure and backdrafting. The upper opening is placed close to the ceiling (within 12 inches) so that air can readily move from the space above into the room as hot air and combustion byproducts rise. This high opening ensures a dependable supply of air for combustion from the top portion of the space and helps maintain proper ventilation even as the room heats. The lower opening near the floor then provides cooler air from below, creating a natural two-way flow that keeps the appliance fed with oxygen and reduces the chance of issues like incomplete combustion. So, the requirement that the upper opening be within 12 inches of the ceiling is correct.