What type of ducts are prohibited for clothes dryer exhaust systems?

The reason flexible ducts are prohibited for clothes dryer exhaust systems primarily revolves around safety and efficiency concerns. Flexible ducts are more prone to accumulate lint, which can create a significant fire hazard. The bends and folds in flexible ducts can trap lint, reducing airflow and increasing the risk of overheating.

Additionally, flexible ducts are typically not as durable as rigid ducts, making them more susceptible to damage over time, which can lead to further lint buildup and potential failures in the exhaust system.

In contrast, rigid ducts provide a smooth interior surface that allows for better airflow and minimizes the chances of lint buildup. They are generally more robust and maintain their shape over time, ensuring that the exhaust system operates effectively and safely.

Choosing the appropriate duct materials and types for dryer exhaust systems is critical to comply with the mechanical code and to ensure the safety and efficiency of the appliance.