Type B vent pipe must be kept at least how far from combustible materials?

Type B vent pipes are designed to safely vent flue gases from appliances that burn gas, ensuring that the heat and gases produced do not pose a risk of igniting surrounding materials. The established safe distance is crucial to prevent potential fire hazards. Keeping Type B vent pipes at least one inch away from combustible materials provides enough clearance to allow for proper ventilation and reduces the risk of heat transfer that could ignite flammable substances. This distance accommodates thermal expansion and provides a safety buffer against any potential issues that may arise during the normal operation of gas-fueled appliances.

In contrast, other distances mentioned in the options either exceed or do not meet the necessary safety standards set by codes and regulations for vent piping. Understanding this clearance is vital for HVAC professionals to ensure compliance with safety standards and to maintain a safe working environment.