Which option corresponds to a valid minimum rectangle fresh air intake size?

Which option corresponds to a valid minimum rectangle fresh air intake size?

• A. 3 sq. Inches
• B. 6 sq. Inches
• C. 9 sq. Inches
• D. 12 sq. Inches

Answer: (D)

Ensuring adequate combustion air is the main idea here. A rectangular fresh air intake must provide a minimum cross‑sectional area so the appliance in a confined space can draw enough air without creating a negative pressure that could backdraft or starve the burner. For a rectangular opening, area = length × width. The minimum required area in this context is 12 square inches, which corresponds to a 3-inch by 4-inch opening. That’s why 12 square inches is the correct choice—the other options (3, 6, or 9 square inches) fall short of the minimum and wouldn’t meet the standard requirement. Larger openings are acceptable if space and installation allow, but the key point is meeting or exceeding that 12 in² minimum.

Ensuring adequate combustion air is the main idea here. A rectangular fresh air intake must provide a minimum cross‑sectional area so the appliance in a confined space can draw enough air without creating a negative pressure that could backdraft or starve the burner.

For a rectangular opening, area = length × width. The minimum required area in this context is 12 square inches, which corresponds to a 3-inch by 4-inch opening. That’s why 12 square inches is the correct choice—the other options (3, 6, or 9 square inches) fall short of the minimum and wouldn’t meet the standard requirement. Larger openings are acceptable if space and installation allow, but the key point is meeting or exceeding that 12 in² minimum.