I am in the process of clearing out old random wires from my 100 year old house (think multiple layers, modern, knob and tube and everything in between). In the process of doing this, I tried to remove a knob and tube circuit that disappeared into an air duct. I turned off the breaker feeding it and cut the wires before they entered the duct. Why is the wiring being traced through an air duct? You'll have to ask someone from 100 years ago.
I then went to the panel to disconnect the wires completely from the breaker (leaving the loose in between pieces in the air return, as I don't want to take that apart). The hot wire is easy to identify being connected to a specific breaker. However, it enters the panel by itself, as a single cloth wrapped conductor not linked in any way to the neutral. The neutral is one of 30 other neutral wires entering the panel, and I can't easily see which one it is. Is it safe to leave the neutral wire that is buried in the air duct connected to the neutral bar, or should I really unearth it so I can fully remove it from its panel connection.