Me trying to follow a wall containing a heating duct from my second floor office down to the basement to figure out if I can run a network wire through it

It would be easier if, like, the heating duct went straight to a vent. But, the heat vent connects to a hose that heads off sideways into the wall.

@wohali Yeah, I'd like to run the cable alongside the duct, rather than inside it.

I'd read that it's okay code-wise to go inside a cold air return, but not an actual heating duct. Though, I do have plenum-rated cable just in case.