More 21++ Gas Fireplace Black Soot
More 21++ Gas Fireplace Black Soot. If you see thick black marks on. Is black soot from gas fireplace dangerous? What you're looking at, actually, is a fine coating of black soot on the surface, which happens when the gas in your fire pit or fireplace isn't burning properly. The air part of the fire triangle is also the problem when the glass doors on your gas fireplace start turning black.