Defra exempt stoves are designed for use in smoke control areas in the UK. These Defra exempt stoves have been independently tested to meet strict criteria on emissions, which then qualifies the stove to be exempt from the requirements of the Clean Air Act.
If you live in a smoke-controlled zone, then the only wood burning domestic heating appliance it is legal to install and burn, is a Defra exempt stove.
It is worth noting that the particulate matter (PM) emission limits for Ecodesign compliant wood burning stoves and fireplaces is 55% lower than for Defra Exempt stoves.
All clearSkies Level 3 and above certified appliances are also Defra Exempt.