Appliance Exemption from Section 21 of the Clean Air Act 1993 (Smoke Exemption) What is the Clean Air Act (brief history)? In response to the Great Smog of 1952, the British Parliament introduced the Clean Air Act 1956. This act legislated for zones where smokeless fuels had to be burnt and relocated power stations to rural areas. The Clean Air Act 1968 introduced the use of tall chimneys to disperse air pollution for industries burning coal, liquid or gaseous fuels. The Clean Air Act was updated in 1993 and can be reviewed online as legislation Clean Air Act 1993. The biggest domestic impact comes from Part III, Smoke Control Areas, which are designated by local authorities and can vary by street in large towns. Today, any solid fuel combustion appliance burning a non-authorised fuel requires exemption before use in UK smoke control areas. As part of Bio-Nordicâ€™s product certification support service, we are able to assist your company with achieving smoke exemption status for your range of biomass boilers.