When shut, Each individual close rests around the one beneath it. This damper type finds its Most important use in ducts with preset airflow. Handbook dampers are modified by hand and are generally used in more mature HVAC techniques. They are less popular nowadays due to improved efficiency and usefulness https://air-control-dampers-for-h24456.thechapblog.com/35757917/helping-the-others-realize-the-advantages-of-air-control-dampers-for-hot-climates