Soot from painted basement ceiling.
I had my basement ceiling (unfinished wood trusses, etc.) spray painted black a month ago. I am still getting a fine layer of black soot on the horizontal surfaces. What is causing this and how do I fix it?
Most likely the soot is from the overspray when spraying the paint. This would have dried as a powder and is sitting on the horizontal surfaces of the trusses. When disturbed it comes loose and falls as a fine powder.
Try to vacuum off the trusses to remove this powder.