They allow airflow to move in one route and to circumvent it in the alternative direction. They may be created from corrosion resistant extruded aluminum. Design 1290F is an economical true spherical hearth damper designed and capable for place-of-origin hearth containment in which spherical ductwork passes by means of steel https://heavydutystainlesssteelda12345.blogchaat.com/37080387/a-secret-weapon-for-heavy-duty-stainless-steel-damper-manufacturers