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The testing regime itself is another obstacle to real improvement. Yes, stoves are getting better, and by 2022 those sold in Europe will have to meet Ecodesign standards that set limits on how much smoke they can produce.
However, as with diesel vehicles, there is a very large disparity between test performance and the smoke that comes from stoves in the real world.
Stoves are tested in idealised conditions using dry wood burnt for just an hour or so rather than the variety of wood that people use at home with frequent refuelling and adjustment to keep a fire going all evening.
So the results from laboratory tests have been nothing like results from those same wood-burners when they were tested in normal houses – and produced ten times as much pollution.
Some days the emissions were close to those of the laboratory test and at other times they would be as much as 16 times higher.
There has been huge variability in results even from the same stove, and it was a puzzle to find out why. Using wet wood appears to be one factor that increases the pollution; closing the air vents on the stove is another.
The biggest factor, though, is the person who lights the fire and the skill with which he or she does so. (Some countries have introduced videos and classes aimed at encouraging the best wood-burning techniques, such as lighting their fires from the top of the stacked wood and using plenty of kindling.
There is worrying evidence from air- quality testing carried out at a bowling club in the small New Zealand town of Wainuiomata, near Wellington.
As expected, the town’s air was full of wood smoke throughout the winter, but the smoke contained arsenic at a level 50 per cent greater than the legal limit in Europe.
The only possible explanation was that people were burning construction timber, treated with a preservative known as chromated copper arsenate (CCA).
New Zealand scientists rapidly found that it was not just a local problem. Treated wood was being burnt everywhere. Arsenic and lead were found in the air of suburbs of the Greek capital Athens, suggesting that people were burning construction waste and old painted wood. This is inevitably happening in Britain, too.
Ask me about food.
How Permies.com Works (lots of useful links)
Fine particulate matter, the very small particles that make up smoke and soot, may be the most
dangerous component of wood smoke pollution. The most harmful particles are those ten
microns or less in diameter (a human hair is approximately 70 microns in diameter). These
particles can easily be inhaled deep into the lungs, collecting in the tiny air sacs (called alveoli)
where oxygen enters the blood, causing breathing difficulties and sometimes permanent lung
damage. Inhalation of fine particulate matter can increase cardiovascular problems, irritate lungs
and eyes, trigger headaches and allergic reactions, and worsen respiratory diseases such as asthma,
emphysema, and bronchitis, which could result in premature deaths.
