Replace fiberglass insulation?

[u/ruttman31]

I recently removed a built in gas fireplace insert from the basement, exposing the insulation that you see here. Is the darker spots mold or is that possibly just dirt from the fireplace itself? Should this insulation be replaced?

[u/General-Mission6960]

I would air seal what you can while it's open. The dark spots is dust, meaning dirty air movement. That's why you should seal up what you can.

[u/SaoirseYVR]

It more than likely is dust collection from air leakage through the wall. If you are concerned replace. Insulation is fairly cheap.

[u/Subat0micR0gu3]

It'a dirt from air movement. I'd look clpsure at the exterior part of the wall in those areas and see if you can see any openings. Then seal them.

[u/hahayes234]

The coax and the idk maybe data line will need relocated, maybe the air flow is coming from where those lines enter. I don't think I would worry about the insulation