What is the maximum length of a clothes dryer exhaust duct from the dryer to termination?

The maximum length of a clothes dryer exhaust duct from the dryer to the termination point is typically set at 25 feet, as specified in various building codes and standards including those from the International Residential Code (IRC). This limitation ensures that the exhaust system operates efficiently, reducing the risk of lint buildup and the potential for overheating, which can lead to fire hazards.

The 25-foot length is calculated based on using 4-inch diameter ducting and considers the necessary bends and turns that could obstruct airflow. Each turn or elbow can add to the effective length of the duct, so if the duct has bends, the actual allowable straight run may need to be shorter. Proper termination of the duct outside the building is essential to ensure that moist air, lint, and heat are expelled effectively.

When calculating the maximum length, it's important to adhere to these guidelines to maintain dryer performance and safety. Using an exhaust duct longer than the recommended length can result in inadequate venting, leading to increased dryer run times, potential malfunctions, and increased risk of fire due to lint accumulation.