What is the minimum clearance from the flue outlet for gas-fueled appliances?

• A. 12 Inches
• B. 24 Inches
• C. 18 Inches
• D. 6 Inches

Answer: (C)

Clearance around a flue outlet is about preventing heat from reaching nearby combustibles and ensuring the exhaust can vent freely. Gas-fueled appliances emit hot gases, and keeping a safe gap reduces the risk of ignition or damage to adjacent materials while also allowing proper airflow for venting. An 18-inch buffer is a common minimum because it provides a reliable safety margin without being excessively large, balancing fire safety with practical space in typical rooms. Smaller distances increase the chance of heat damage or unintended heat transfer, while larger gaps are generally not required by standard practice unless a specific appliance or code calls for it. So, 18 inches is the standard minimum.