The municipal inspector who issues Certificates of Occupancy when
ownership changes or apartments get new tenants, failed me because he
saw a "vent" in the garage ceiling. The potential problem is that any
carbon monoxide in the garage can be sucked up by the vent when the heat
or a/c is running and be distributed throughout the house. He wants me
to cover it with metal or sheetrock and caulk around the edges.

Problem is, that it is really a supply register. When I looked in the
attic, I could clearly see that the duct supplying it came directly from
the plenum (just above the evaporator) that feeds the other ducts to the
rest of the house.

I removed the register and found that someone had taped its openings
shut, so air couldn't flow either way through it. I sent photos to the
inspector of the register showing how it was taped shut. I also taped a
small piece of facial tissue to the ceiling and turned on the a/c. It
fluttered in the incoming airstream, and was not sucked upwards as it
would be if this were a return.

I wanted to just return the taped-shut housing the way it was. But the
inspector is being hard-assed. He doesn't want to see anything - supply
or return - in the ceiling. I do NOT think he's looking for me to slip
him a few bucks.