What must clothes dryer exhaust ducts be constructed from according to the mechanical code?

Clothes dryer exhaust ducts must be constructed from metal according to the mechanical code because metal ducts are durable, fire-resistant, and effective in withstanding high temperatures and pressures generated by the dryer during operation. Metal materials like aluminum or galvanized steel provide a smooth inner surface that allows for effective airflow and minimizes lint buildup, which is crucial for maintaining efficiency and preventing fire hazards.

Other materials such as plastic and fiberglass are less suitable for dryer exhaust ducts because they may not be able to handle the heat generated by the dryer or might negatively affect airflow over time. Wood, on the other hand, poses a significant fire risk and is not compliant with the safety standards required for dryer venting. Using metal for exhaust ducts not only aligns with safety regulations but also ensures the longevity and effective operation of the dryer system.