To what standard must duct installations comply for makeup air ducts?

Makeup air ducts must comply with specific requirements related to the materials used in their construction to ensure safety and functionality. The correct answer highlights that these ducts must either be made of noncombustible materials or be listed for the intended application. This is crucial because makeup air ducts are often installed in environments where they may be exposed to heat or combustion sources, which could pose a fire risk if the materials are not appropriate.

Using noncombustible materials helps prevent ignition in the event of a fire and contributes to the overall safety of the building. Alternatively, ducts that are listed for specific applications have been tested and certified to meet rigorous safety standards, ensuring they can withstand certain conditions without compromising safety. Thus, adherence to these requirements is essential for mechanical systems that support proper ventilation and prevent hazardous situations in buildings.