Firstly, when burned, damp wood produces more smoke than dry logs. This includes tiny particulates known as PM2.5 that are more harmful than bigger flakes of soot because they can penetrate deep into the respiratory system and bloodstream. UK government figures show wet wood (and coal) is responsible for 38% of PM2.5 pollution in the UK – three times as much as road transport. Secondly, burning damp logs produces a heavy smoke that condenses onto the cooler sides of your flue or chimney, producing tar and acidic residues which cause thick deposits to build up. This is a major cause of chimney fires and these compounds also cause damage to the stove and flue. Thirdly, and on top of all this, there's then the additional and otherwise avoidable costs of redecorating your home following any damage done due to burning wood that's not seasoned enough.