In a confined space, the upper opening that supplies combustion air to a fuel-burning appliance must be within 12 inches of the ceiling.

• A. True
• B. False
• C. Depends on appliance
• D. Not specified

Answer: (A)

In a confined space, providing combustion air from outdoors relies on two openings to create a natural air path: one near the bottom and one near the top. The upper opening must be within 12 inches of the ceiling. Placing the high opening close to the ceiling takes advantage of buoyancy—cool outdoor air can enter from below, circulate through the space as combustion uses up oxygen, and any warm air or combustion byproducts rise and can exit through the upper path. This setup helps maintain a steady supply of fresh air to the appliance and prevents negative pressure that could pull combustion gases back into the space. So, the statement is true.