Smoke is produced when fuels are burnt to generate heat, electricity and locomotion. Most fuels burnt are fossil fuels, including coal, oil and gas. When fossil fuels are burnt, the smoke given off is made up largely of tiny particles of unburned carbon.
Smoke was a common pollutant in Britain during the 19th and early 20th centuries, at the height of the Industrial Revolution. A lot of smoke came from domestic coal burning for heating purposes. Consequently, smoke pollution was worst during the winter months. Smoke and sulphur dioxide pollution would mix with fog to produce smogs.
The 1926 UK Smoke Abatement Act reduced smoke emissions from industrial sources. The Clean Air Acts of 1956 and 1968 made it illegal for smoke to be emitted from homes within Smoke Control Areas. Smokeless fuel may be used which produce little or no smoke when burnt. Examples are natural gas, anthracite (a very pure form of coal) and specially developed fuels such as Coalite. Today, most people living in mainland Britain, particularly in urban areas, have gas central heating, and smoke emissions from domestic sources are very low.