Any combustible wall or ceiling finish exposed between the edge of a fixture canopy or pan and an outlet box shall be:

Combustible wall or ceiling finishes that are located between the edge of a fixture canopy or pan and an outlet box are required to be covered with noncombustible material to ensure safety. This regulation is crucial in minimizing fire hazards, as combustible materials can easily ignite when exposed to heat or sparks from electrical fixtures. Noncombustible materials, such as certain metals or fire-rated drywall, serve as a barrier that prevents the spread of flames, helping to protect the surrounding structure and occupants.

Other options like reinforcing with additional materials may not adequately address the fire risk, while leaving the surfaces untreated poses a direct danger. Painting over with fire-resistant paint could provide some level of protection, but it does not create as effective a barrier as the thorough coverage provided by noncombustible materials. Therefore, the requirement to cover such finishes with noncombustible material is a key safety measure in electrical installations.