The nights are fair drawing in and on those chilly November evenings, what better than to wrap up warm with a steaming mug of hot chocolate while throwing another log on the stove? The Danish and Norwegians call this Hygge! Embracing that feeling of cosiness! In Old Norse, the term hyggia means “to think”.
Should we take that as a hint that maybe we need to think a little more about whether these log burning stoves which are so lovely in a cottage in the countryside, are suitable for those cold winter evenings in a city?
If you venture out on a chilly evening in the town to go for a run or walk the dog, it’s becoming all too common to be breathing in smoky air. And with people looking for cheaper ways to heat their homes this winter, they may well be thinking that burning cheap sources of wood is a good idea. But is it?
We have had air pollution from industrial and domestic sources ever since the Industrial Revolution. This year marks the 70th anniversary of the “Great Smog” which hit the city of London for five days in early December when a particular weather system of cold air settled over London and combined with smoke from coal burning factories and exhaust from diesel vehicles this led to a thick dense “pea souper” fog with very low visibility. It resulted in thousands of deaths from pneumonia and bronchitis in a matter of days. In some parts, people could not even see their own feet and reportedly a herd of cattle choked to death at Smithfield market. Over the years, Glasgow and other cities also experienced these “pea soupers”.
The consequence of this moment in history was that the Clean Air Act was passed in 1956 which sought to restrict the burning of coal and offered homeowners grants to use alternative heating sources such as natural gas and electricity. It also established smoke free areas in cities.
How big a problem is pollution?
Pollution is still a worldwide problem and figures from the World Health Organisation are staggering, with up to 20% of deaths worldwide being attributed to air pollution from the burning of fossil fuels.
Another shocking statistic is that WHO data show that almost all of the global population (99%) breathe air that exceeds the WHO guideline limits and contains high levels of pollutants, with low- and middle-income countries suffering from the highest exposures. (Air pollution (who.int))
How does the smoke affect your health?
The latest trend in the UK is to have an open fire or a wood burning stove. Open any interiors magazine and I guarantee you will see one. But what are the costs of these to our health?
If we look at wood burning stoves in particular, the biggest problem seems to be their production of smoke particles or “particulate pollution”. The biggest smoke particles can be seen by the naked eye, but the most dangerous are the small particles.
These particles divide into ultrafine particles that are under 0.1 micrometres in size (PM 0.1), small particles of under 2.5 micrometres in size (PM 2.5) and the largest which are under 10 micrometres in size (PM 10). By comparison, a human hair is 50 to 70 micrometres in diameter. The smallest of these particles can cross the thin membranes of your lungs, enter the bloodstream and lodge in your organs. They are thought to be responsible for up to 40,000 early deaths a year across Europe.According to the Asthma and Lung UK charity, particulate matter irritates your nose and throat and may be associated with more severe symptoms in people with asthma. It results in more people with lung conditions and heart conditions being admitted to hospital. It can also lead to early deaths from lung and heart disease. There’s also evidence that long-term exposure to particulate matter can contribute to the development of lung cancer and possibly asthma.
The finest particles can travel long distances in the air. They can come from a variety of sources including industry and agriculture. But two sources that we have more control over are the choices we make with regards to transport and domestic heating.
Where there’s fire there’s smoke
With regards to wood stoves, it has been found that there is a certain level of PM 2.5 particles in the air inside and outside of our homes whether you have a stove or not. A survey in 2019 in USA found that homes without stoves had a median PM 2.5 of 6.65 µg/m3 whilst homes with stoves were only a fraction higher at 7.98 µg/m3 .
If you have a modern wood burning stove, the stove sucks air from the room, drawing particles into the fire, up the chimney and outside. But by how much are they affecting the outside air?
According to Government reports, wood burning is believed to contribute around 17% to small particle pollution (PM 2.5) while in comparison road transport is responsible for 13% of particle pollution. (Emissions of air pollutants in the UK – Particulate matter (PM10 and PM2.5) – GOV.UK (www.gov.uk)). Though the good news is that the trend in particle pollution is very much downwards since the 1970s. But we may just need to keep an eye on these trends to ensure we don’t start that upward climb again towards more polluted air.
With regards to clean air, DEFRA classes the cleanest and freshest air as having PM 2.5 levels under 11 µg/m3. The World Health Organisation has a long term target of not exceeding annual average concentrations for the PM 2.5 particles of 5 µg/m3 and for the PM 10 particulate matter, the target is an annual level of 15 µg/m3 . My local area just came in under that target at 4.8 µg/m3 for PM 2.5 but other areas nearby had higher annual figures so did not make the target. And data for particular days in my area hit as 18 µg/m3.
To keep track of the levels of pollutants in our cities, there are air quality monitoring stations across Scotland.
Air Pollution is monitored
You may have seen air quality monitoring stations positioned across Scotland, particularly in urban areas and these are monitored by Air Quality Scotland. The measured levels of pollutants for your local area, such as particulate matter and gases such as nitrogen dioxide, can be viewed online. The data is fascinating to explore, and you can view it in a variety of ways.
In the UK such air monitoring services use the index and banding system approved by the Committee on Medical Effects of Air Pollution Episodes (COMEAP) and on the November evening when I was writing this article, all 100 sites in Scotland were measuring at Low Levels of air pollution, which is good news but perhaps it may not pick up more localised pockets of pollution?
If you have a respiratory condition, you can sign up for the Air Quality Know and Respond Service (https://www.scottishairquality.scot/know-and-respond) which gives warnings when air pollutant levels are expected to be higher.
Stove design must be DEFRA approved
From 2022, all new stoves that are installed across Europe must be of the new Ecodesign. According to the Stove Industry Association, the latest Ecodesign Ready stoves have 90% fewer particle emissions than an open fire and are an improvement over the older designs of stove. Ecodesign stoves must adhere to strict criteria around emissions and efficiency. They use less fuel for the same energy output, so produce fewer emissions and will cost you less in fuel costs.
If you plan to install a stove, you can check with your local council to see if you live in a smoke control area. Planning permission may be needed before installing a stove and in smoke control areas and the stoves must be DEFRA approved. As well as considering stove design, you must consider the fuel type that you plan to use.
If you live in a smoke control area, you can check the details about certain fuels here:
If using wood logs, you must also ensure they are properly dried out – this takes at least a year. The moisture content should be down below 20%. You can check the weight and density by hitting two logs against each other and if they make a hollow sound, they are ready for burning. Hardwoods such as oak, ash or birch make for better burning logs, coming from trees which grow slowly. Softwoods such as pine or spruce grow more quickly, are less dense and not so good for burning.
If people are not burning the appropriate fuels and are causing smoke, they can be reported to local councils.
Can we consider a wood stove to be environmentally friendly?
Many folks have bought into the wood burning stove experience, imagining that it is indeed more natural, and that wood can be considered as a renewable resource. However, it does not take long to burn some logs. It takes much longer for that tree to grow. So surely, we should also be planting trees more extensively in Scotland?
What future for stoves?
So clearly there are some issues to be considered before throwing that extra log on the stove! The health effects of pollutants are very worrying and wood burning is a contributor to this. However, the air quality monitoring across Scotland records low average levels of pollution but there are still many areas not hitting the WHO target and on certain days the pollution levels can be worrying.
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