What is a plausible minimum dimension for a combustion air inlet screen?

• A. 1 inch
• B. 3 inches
• C. 9 inches
• D. 6 inches

Answer: (A)

Ensuring adequate combustion air is available for the appliance is essential for safe and efficient combustion. An inlet screen serves to keep debris and pests out while still allowing air to flow freely. If the opening is too small, the air supply can become restricted, causing incomplete combustion and potential safety hazards like carbon monoxide buildup. Among common, practical guidance, a 1-inch opening provides the smallest dimension that can reasonably deliver enough air for typical residential appliances while still letting the screen do its job. Larger openings—3, 6, or 9 inches—would supply more air but aren’t necessary to meet a plausible minimum; they’re simply larger options that may be used in bigger installations.