What is the minimum air space clearance to combustibles for a masonry chimney located inside the building or within the exterior wall?

What is the minimum air space clearance to combustibles for a masonry chimney located inside the building or within the exterior wall?

• A. 2 inches
• B. 1 inch
• C. 1/2 inch
• D. 0 inches

Answer: (A)

Two inches. That gap provides a protective buffer between the hot masonry chimney and any surrounding combustible materials, reducing heat transfer by conduction and radiant heat to prevent ignition. Smaller gaps would let heat reach wood framing or insulation and could pose a fire hazard. A zero clearance would place combustibles in direct contact with the chimney, which is not allowed.

Two inches. That gap provides a protective buffer between the hot masonry chimney and any surrounding combustible materials, reducing heat transfer by conduction and radiant heat to prevent ignition. Smaller gaps would let heat reach wood framing or insulation and could pose a fire hazard. A zero clearance would place combustibles in direct contact with the chimney, which is not allowed.