A Black Substance That Comes From Burning Wood. Chimney soot is fine black or dark brown powder formed due to incomplete combustion of wood or coal in a confined place. Hence it can be correctly referred to as the byproduct of fireplace combustion.

Chimney soot is fine black or dark brown powder formed due to incomplete combustion of wood or coal in a confined place. Soot is formed in a temperature lower than 284 degrees. What is a black substance that comes out of burning wood?