What is the typical minimum clearance required between a duct and non-combustible materials?

The minimum clearance required between a duct and non-combustible materials is typically 1 inch. This distance allows for proper airflow around the duct while also accommodating thermal expansion and contraction. Maintaining this clearance is crucial to ensure safety and efficiency in heating, ventilation, and air conditioning (HVAC) systems.

The 1-inch gap reduces the risk of heat transfer to surrounding materials, thereby preventing potential issues like overheating and providing a buffer zone that supports proper ventilation. This standard is often referenced in building codes and manufacturers' specifications, highlighting its importance in construction and installation practices for sheet metal ducts.

Several other options mentioned higher clearances, which might be excessive for non-combustible materials according to accepted practices and codes, indicating that while safety is paramount, the standard for non-combustible materials specifically allows for a closer proximity than those suggested by other choices.