What is the minimum clearance from the duct to interior surfaces that are noncombustible or limited?

What is the minimum clearance from the duct to interior surfaces that are noncombustible or limited?

• A. 4 inches
• B. 8 inches
• C. 6 inches
• D. 12 inches

Answer: (D)

The fundamental idea is to create a protective buffer between ductwork and surrounding interior surfaces to limit heat transfer and allow for safe installation, inspection, and firestop containment. When interior surfaces are noncombustible or have limited combustibility, a specific minimum distance is still required to ensure radiant heat from the duct won’t affect those surfaces and to provide space for any required firestop materials and maintenance access. The minimum distance specified is 12 inches, which provides adequate protection and code compliance. Smaller clearances do not meet these safety and installation requirements.

The fundamental idea is to create a protective buffer between ductwork and surrounding interior surfaces to limit heat transfer and allow for safe installation, inspection, and firestop containment. When interior surfaces are noncombustible or have limited combustibility, a specific minimum distance is still required to ensure radiant heat from the duct won’t affect those surfaces and to provide space for any required firestop materials and maintenance access. The minimum distance specified is 12 inches, which provides adequate protection and code compliance. Smaller clearances do not meet these safety and installation requirements.