I have a two story commercial building that is creating salt grain size (sometimes larger) black moist dust bunnies. I use dust bunnies, because not sure what else to call them.
I do not have a picture at this time.
The dust bunnies are only on the 2nd floor ... only in the northwest corner private offices and are coming out of the bar slat single direction supply registers that are placed in the ceiling next to the exterior walls.
The large 4 way supply registers in the large cubical offices have no problem.
At this time, I am just trying to come up with a hypotheses, so I can start somewhere with testing.
I was just wondering if any of you have already run into this before or have a hypotheses of your own with this limited amount of information.