What is the required clearance to combustibles for a class B vent?

The correct requirement for clearance to combustibles for a class B vent is 1 inch. Class B vents are specifically designed for venting gas appliances that produce combustion gases at relatively lower temperatures compared to other vent types. This lower operating temperature is key to determining the necessary distance from combustible materials.

When installing a Class B vent, maintaining a 1-inch clearance helps prevent heat transfer that could lead to ignition of nearby combustible materials. The National Fuel Gas Code (NFPA 54) outlines these safety clearances to ensure proper venting and minimize the risk of fire.

Other options represent clearances that are typically applicable to different types of vents or installations. For instance, Class A vents or double-wall chimney systems might require greater clearance due to higher operating temperatures or different construction materials. It’s important to adhere strictly to these clearance requirements to ensure safety and compliance with local codes and regulations.