Electrical wiring running parellel and through ductwork?
I keep finding interesting things in this rental home. The basement has an open ceiling in most areas. The "duct" leading to the external compressor is sheet metal nailed over a pair of floor joists to turn them into a duct.
However, it appears than when it was installed, the installer didn't worry about the electrical wiring that was already going through those joists. There are about eight wires which go through those joists, parallel to them, and most of them are through holes that aren't sealed well.