DEFRA is the UK Government Department of the Environment, Food and Rural Affairs which regulates smoke emissions under the Clean Air Act 1993.
The Clean Air Act 1993 prohibits emissions of smoke within smoke control areas, unless using an exempted appliance or using an authorised smokeless fuel i.e. fuels that have passed tests to confirm that they are capable of burning in an open fireplace without producing smoke. The Clean Air Act prohibits emissions of dark smoke from any chimney.
For a list of Smoke Control Areas visit http://www.uksmokecontrolareas.co.uk/locations.html
Defra approved or “exempted” wood burners and stoves have passed tests to confirm that they are capable of burning an unauthorised or inherently smoky solid fuel without emitting smoke.
For a list of Exempt Appliances (Approved for use within an Smoke Control Area) visit https://smokecontrol.defra.gov.uk/appliances.php
DEFRA approved or “smokeless” fuels can burn on an open fire without producing smoke.
For a list of Authorised Fuels visit https://smokecontrol.defra.gov.uk/fuels.php