What is the minimum size for a dryer exhaust duct?

The minimum size for a dryer exhaust duct is specified to be 4 inches in diameter. This size is necessary to ensure optimal airflow and efficiency when venting a clothes dryer. A larger diameter duct facilitates proper exhaust of moist air, lint, and other particles, which helps to prevent blockages that could lead to malfunction or even fire hazards. Additionally, a 4-inch duct size strikes a balance between minimizing resistance to airflow while also accommodating the amount of air a typical household dryer requires for efficient operation. When exhaust ducts are undersized, it can lead to increased drying times and force the dryer to work harder, potentially leading to premature wear or inefficiency. Following this code requirement helps maintain safety and performance standards for dryer operations.