Why does DEFRA certify wood stoves without addressing the flue technology that can aid in alleviating the incomplete combustion issue? The wonkiness about the standardisation is that the exhaust is largely ignored. Chimney cowls are only assumed to stop wind, rain and snow. They are not recognised in the standards as an aid against negative pressure/ down draught. Does this typical wood stove issue in winter contribute to particulate pollution, regardless of appliance certification? Yes. Of course it does. The American EPA and the NGOs they help fund speak truly about atmospheric inversion trapping wood smoke, but untruly about the heating method being at fault. The same atmospheric condition is helping to creating their fine particulate matter/ soot by putting negative pressure on the appliance's exhaust pipe. It's fixable. There are products available now that are effective. The standards need updating to include the whole heating system. In doing so they will do better at identifying the smoky and creosote causing issues. Once a more accurate assessment has been performed on the entire self-suficient and sustainable heating method - then you can give the regulators something more accurate to regulate. Finish the job of appliance standards first then look at the best and worst wood species - list them. List the materials people cannot burn due to proven toxicity - PM is far too generalised and is a phantom maybe/ maybe not toxin to attempt regulation with.