Smoke residue is a term used to describe the byproducts of combustion, such as burning wood or coal. The two most common components of smoke residue are TAR and SOOT. TAR is a dark, viscous liquid composed of hydrocarbons and other organic compounds, while SOOT is a black powdery or flaky substance made up of carbon particles. Both TAR and SOOT can be hazardous to human health if inhaled, and can cause respiratory problems.