What type of duct material is required for makeup air ducts?

The requirement for makeup air ducts to be made from noncombustible materials or materials that are listed for the application is based on safety standards outlined in mechanical codes. Noncombustible materials provide a safety advantage by reducing the risk of fire within the duct system, as these materials do not ignite or contribute to the spread of fire. Similarly, materials that are listed for the specific application have been tested and certified for safety, ensuring they perform adequately in the intended environment.

Having noncombustible or listed materials ensures compliance with local fire and safety codes, which are crucial for maintaining safe building conditions, especially in areas where large volumes of air may circulate, potentially bringing with it sources of ignition. This requirement is particularly important in commercial and industrial settings where the volume of makeup air can be substantial and the risk associated with fire needs stringent considerations.

While options like combustible materials or flexible materials might seem feasible, they do not meet the same safety standards required for duct work, particularly in the context of makeup air, where adherence to noncombustible criteria is essential to minimize fire risk. The use of "any material" is too broad and does not adhere to safety regulations expected in mechanical installations.