Your contractor is a criminally dangerous idiot. Neither the wiring nor that foam insulation is permissible in the duct. The only exception would be for high temp (e.g. Teflon) insulation. I

Bruce, it did pass inspections. Thats why I'm not sure if its allowed or if the inspector missed it. This is only in one place (as far as we know). And we only found it now because we decided to do some extra work in the basement. Would not have even known about it otherwise.

Whoa, that's really ugly.

Here's a true story for you. Several years ago I walked down into the cellar one evening and heard an odd humming noise. After some investigation I found that some of our old original rubber-and-cloth knob and tube wiring had been run over, into, and through a cold air return duct. The wires were unsupported and had no protection at all where they passed through the sheet metal, no ceramic tubes, not even loom.

This must have been done when the heating system was upgraded and the cold air return was installed, probably between 10 and 25 years earlier, before I owned the house.

Over the years, the duct's vibration had worn the insulation from the wires where they touched the sheet metal. They also had sagged so they were touching the top of the duct (probably the reason for the humming).

Fortunately, the copper actually touching the duct was the grounded (neutral) conductor. But the hot side wasn't far behind.

If I hadn't found that, we might have had a fire or electrocution.

So, no, what you have there isn't right; and yes, it's hazardous.

I think (I'm sure Ron will correct me if I'm wrong) that it's still permissible to route NM cable through a cold air return if it's protected by thinwall conduit or something equivalent. But IMO it's best to avoid it entirely if you can.

In general any wiring of any type (including low voltage and phone and data cable) that passes through an air handling space is supposed to be "plenum rated." IIRC, that has to do with its flame resistance and smoke production when heated.

Please get that fixed.

I agree with DavidR. You might get by with metal conduit but even then it’s sloppy and unworkmanlike

it did pass inspections. Thats why I'm not sure if its allowed or if the inspector missed it.

He missed it. It probably wasn't visible since it's in the duct and you only noticed it because you happened to open it up for some reason.

Your contractor or his subs were trying to pull a fast one and hope that nobody noticed. Then the contractor tried to BS you when he was caught.

Insist on getting this fixed. Inform the inspector so that he knows what kind of contractor this is.

Looks like we are looking at returns here. If it was supply that would be more of an issue. The biggest issue I see is the metal exposed ends near the electrical. There should be some form of bushing or conduit around the electrical to protect it from the duct. This is akin to running electrical through metal studs.

At least they attempted to get a good seal for you... Some could care less.

Electric before duct runs will get you this, can easily happen. Then you get tin bashers trying to work around the wires, although they should know to protect the wire.