When you see flames, the black thing that you may notice is called soot. Soot is made up of carbon particles that are incompletely burned fuel. When there is not enough oxygen for complete combustion to occur, soot forms.
Soot can be harmful if inhaled because it contains carcinogens. It can also cause respiratory problems and aggravate conditions like asthma. In addition to being a health hazard, soot can also stain surfaces and clothing.
If you have a fire in your home, be sure to open windows and doors to ventilate the area and get rid of the soot as soon as possible. A professional cleaning service can also help remove soot from your home.