Ducts that penetrate a private garage wall must be constructed of which material?

Ducts that penetrate a private garage wall must be constructed of sheet steel because this material provides the necessary fire resistance and structural integrity required for such installations. In the event of a fire, sheet steel ducts can withstand higher temperatures without failing, reducing the risk of fire spreading from the garage to the rest of the building.

The use of sheet steel also complements the mechanical code's emphasis on durability and safety in areas that may be exposed to flammable materials or where the risk of fire is elevated, such as in a garage. Furthermore, metal ducts are more suitable for maintaining air quality and preventing moisture problems that can arise with other materials over time.

Using materials like plastic, wood, or fiberglass for ducts in private garage walls does not meet the stringent safety requirements. These materials may not provide adequate resistance to heat and could compromise safety standards when installed in a fire-prone area.