What is the minimum atmospheric vent size (in inches) of a 2 inch fuel line in a single burner boiler system?

• A. 1 inch
• B. 3 inches
• C. 2 inches
• D. 4 inches

Answer: (C)

In this situation, vent sizing follows the rule that the atmospheric vent must be at least the same diameter as the fuel line to avoid restricting venting of air and vapors. For a 2-inch fuel line, the minimum atmospheric vent size should be 2 inches. Using a smaller vent could choke the venting path and hinder proper fuel flow, while a vent larger than 2 inches meets the minimum requirement but isn’t necessary unless dictated by other codes or equipment specifics. So the minimum is 2 inches.