Can Ductwork Be Tax Credit What Is The Best Way To Fill In And Seal Off Ductwork Under A Concrete Slab?

What is the best way to fill in and seal off ductwork under a concrete slab? - can ductwork be tax credit

I have mold in my pipes under concrete floor of our record and the need to completely fill and seal for the mold is a problem. I save them in the oven seal and earth with three holes. I was told to seal it with concrete. It seems that many concrete it would take to do so. Does anyone offer advice on experience with such things?