What is this stuff on my furnace and should I be worried about it?

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Flyover

Trying not to screw things up worse
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I noticed what looks like some kind of black caulking or sealing material oozing out of a hole in my furnace. It seems like the material is burned and used to cover a space where a PVC pipe enters one part of the furnace, but has come loose and is starting to make its way toward another part of the furnace. I have not noticed any problems with my furnace or smelled any burning.

Picture 1: You can see the PVC pipe entering the furnace.
Picture 2: Close-up of the area I'm talking about.
Picture 3: Detail of what I'm talking about. The black stuff is headed for that slit.
Picture 4: View from "inside" the furnace, looking up. The arrow is pointing to where the black material is just barely starting to drip through one of those slits. It does not appear to have dripped all the way through yet.

I don't know much about how furnaces work. Mine is gas powered.

1. What is that black stuff?
2. Should I do something about it?

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Those in the trade call it "dumb dumb", basically your looking at duct sealant putty.
Basically it's a plyable putty like material to seal air leaks in holes in the furnace to reduce/elimate air leakage.
This should be the same material as you see where you A/C line sets enter the duct where the evaporator coils are inside your plenum.
Sometimes it drys out and will crack and/or loose adhesion.
Readily available at your local heating and cooling contractor supply store.
 
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