I'm wondering if an air return duct added to my HVAC system meets building codes, specifically for fire-rated walls.
I have split system with upflow furnace and air handler in the garage. The furnace and air handler sit on a wooden platform which also serves as the air return plenum box. When I got my AC added, the single 10x20 air return duct was too small so they added a second 14x20 return. The original return inlet is in the front hallway, with the return duct going thought the garage wall. This return is high in the wall, and has about 8ft of duct to the return plenum box. The newly-added return is very short, going through the living room wall, with a very short duct to the plenum box.
My question is regarding penetrations through fire-rated walls, which I assume is what separates my garage from the living room. Since the original return penetrates this wall, I would assume that fire-rated wall penetrations must be allowed for air return ducts, but I suspect there must be some constraints or requirements. So, I am wondering what the requirements are for these ducts when they penetrate a fire-rated wall. I am wondering if I should I have it looked at by a different contractor and redone correctly if it's not right.