Prior to the introduction of the Clean Air Act 1956, the air quality of the principle industrial cities within the UK was much worse than today. The greatest cause of such pollution derived from the burning of coal from power stations, factories and on a large scale, domestic dwellings. The resulting smog became harmful to the health of those living within the cities.

The Clean Air Act 1956 (as amended- 1968) has now been incorporated into the Clean Air Act 1993, but the Dark Smoke (Permitted Periods) Regulations 1958, (which enacted the smoke control provisions of the original 1956 Act). These are still used to define the intensity of smoke emissions in terms of their shade numbers on a Ringelmann Chart.

Under the Clean Air Act 1993, dark smoke is defined as any smoke is defined as any smoke which is as dark as shade number two on the Ringelmann Chart. Black smoke is defined under the Dark Smoke (Permitted Periods) Regulations 1958 as smoke, which is as dark as shade number four on the Ringelmann Chart. The Act prohibits dark smoke emissions from domestic and industrial chimneys and from open burning on trade or industrial premises (including commercially operated agricultural premises). Any industrial furnaces that aren't included within Part I of EPA 1990 may only be installed should they be able to continuously run without emitting any smoke.

EPA 1990 also covers smoke emission controls. Part III of EPA 1990 enables local authorities or individuals to take action against the statutory nuisances that are present or likely to occur, and which are prejudicial to health:

• Smoke emissions from any premises and gases and fumes from domestic properties.
• Dust, steam, smell or other effluvia on industrial, business or trade premises.