What type of dampers are required for dryer exhaust ducts?

Backdraft dampers are essential for dryer exhaust ducts because they allow air to flow out of the duct while preventing backflow from outside into the duct system. This is crucial for maintaining proper ventilation and ensuring that lint and moisture are effectively expelled from the dryer to reduce the risk of fire hazards and maintain efficiency. The backdraft damper opens when the dryer is in use, allowing exhaust to escape, and closes when the dryer is off, preventing outside air from entering the ductwork, which could affect the dryer's performance and energy consumption.

In contrast, automatic dampers are typically used in HVAC systems for ventilation control, manual dampers are adjusted by hand and may not respond quickly to changes in airflow, and pressure relief dampers are generally employed to mitigate pressure buildup in duct systems rather than specifically for dryer exhaust applications. The function and design of backdraft dampers make them the appropriate choice for this specific application.