The term 'SMOKE SOLIDS' can be summarized as a three-letter word, 'TAR'. TAR is a dark, viscous material that is produced when organic matter such as wood, coal, or peat is burned. It is composed of hydrocarbons, organic compounds, and other substances, and is often used in road construction and roofing. TAR is also known to be a major component of cigarette smoke, and is considered to be a major health hazard.