What nominal diameter should the exhaust duct size be for clothes dryers?

The appropriate nominal diameter for the exhaust duct size of clothes dryers is 4 inches. This standard size is specifically recommended because it provides an optimal balance between airflow capacity and minimizing the risk of lint accumulation and blockage. A 4-inch duct allows for efficient venting of humid air and lint produced during the drying process, reducing the likelihood of fires and improving the dryer's efficiency.

Using a larger diameter duct, such as 5 or 6 inches, may not provide significant advantages in airflow for typical residential clothes dryers and could create pressure changes that hinder performance. Conversely, a smaller diameter, like 3 inches, may restrict airflow too much, leading to overheating and potential safety hazards. Therefore, 4 inches is established as the most effective and safe standard for dryer exhaust ducts.