What the cause of this

[mcyr (Marcel Cyr, CMI)]

@sbridges2

This thread needs a knife put in it, The OP could have figured this out on-site, soot or mold? bath vent or dryer vent? I guess he don’t have a ladder. Crazy, why was he there?

I agree, he has been inspecting for 17 years too. Should have verified first what kind of vent it is.
What I see is not mold from my standpoint.

@mgiangarra

Saw this on the exterior around a bathroom and/or laundry vent.

[jolson81 (John Olson)]

Wipe it off and see what it is. The air could be escaping from the sides of the closed damper and our old friend ghosting is present.

[crozell (Charles Rozell)]

@sbridges2

This thread needs a knife put in it

Broken vent is in the post. I guess legalization of marijuana may be a factor for both. LOL

[jfrederick (Joshua Frederick)]

@tglaze

I have yet to see the louvered vents used on other types vents

What? You’ve never seen a bathroom exhaust vent with louvers?

[kshepard (Kenton Shepard, CMI)]

@labstein

My bet is soot from burning candles in the bathroom and running the fan.

Any marmot hair in the bathtub?

[lkage (Larry Kage, CMI)]

@mrodney

Looks melted. Don’t see how a bathroom vent would melt

Flat cheap louvers and hot sun…