I stumbled off of a step ladder and crushed this ductwork. It's in a bathroom and runs along the floor on a concrete slab between joists. The house is 50 yrs old. The ductwork looks like it's galvanized. How do I repair or replace it? The end of the run continues under a wall. Is there a seam on the bottom? If so, I probably ruptured it.
Looks like common 3 1/4" x 14" rectangular tin vent pipe, you should be able to buy it at any good plumbing shop. It sometimes comes with a locking seam along one edge but HVAC professionals often buy non-seamed pieces of various lengths.
You may be able to beat that back into shape and use listed duct tape to patch it up. If not you will need to find the next upstream connection and replace the whole length.