If your HVAC equipment is the heart of your home, then the ducts make up its circulatory system.Air ducts are used to distribute air through out a building, or to exhaust air outside of a building.The most common are:Sheet metal, Fiberglass lined, Fiberboard, and Flex-line air ducts.
Ducts are classified based on the load on duct due to air pressure and turbulence.The classification varies from application to application...