Soot is a black carbon like substance produced during incomplete combustion of wood, oil and other fuels. Soot can consist of acids, chemicals, metals, soils and dust. The particles of soot are extremely tiny, 2.5 micrometers in diameter. This is smaller than dust and mold and its about 1/30 the diameter of a human hair. As you can understand the hazard to health are enormous. Not only it embeds in your lungs but it can also enter the blood stream.
Soot spreads widely and sticks to every surface creating a larger contamination area and it can cause, due to its acidity levels, the surfaces to erode and become pitted, if left untreated, even for a short period of time.