Woodsmoke arises due to the fact that wood is difficult to burn completely, especially under the conditions present in a relatively simple stove. Part of the problem is that there is no such thing as ‘standard wood’: one species of tree burns differently from another and the moisture content and size of the logs also plays a part, meaning that wood burning stoves have to be designed so that they are not too fussy about what goes into them.
The result is that flue gases of wood burning stoves contain some substances which can be categorised as pollutants. These include gases, liquids and even solids. Some of the gases are responsible for the characteristic smell of burning wood, which is not always welcome, especially in congested cities. Liquid pollutants comprise tars and creosote which may condense on the internal walls of the chimney where they will gradually build up and constitute a fire hazard. Finally, solid particles may be carried some distance by the hot air currents in the flue gas but will eventually come to Earth as dust and soot.
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