Televised ducts under slab floor. Ducts are concrete ducts with metal fittings that are rusted and deteriorated. Some of the system has been abandoned and blocked off from the plenum, but the area in the dining room and kitchen are still active on this system below ground. Suggest spin cast mortaring metal fittings on the section that is still active, then spray lining the system with Duct Armor duct lining material to encapsulate the concrete pipes..