Has anyone ran across this before? The photo is kinda far away. I didnt take a close up, but you can see the black around the vent. This is an upstairs bathroom. The fan was running allright with no problems. There was also what appeared to be soot at the ridge vent above the two upstairs bathrooms. The attic was clean what I could see of it. I could’nt get all the way in due to a closet organizer. I do know that the owner is a cigar smoker. If he smokes in the bathroom with the fan on, could this cause this?