Televised ducts under slab floor. Ducts are concrete ducts with metal fitting and connections. Tee connection in laundry room area is heavily rusted as is the plenum. Other metal fittings look good n good condition. Concrete pipe is solid except for the area by the front door where pea gravel is entering g due to Duct dropped at that area. Suggest spin casting tee and plenum then spray lining all ducts to encapsulate the concrete.