Wood burning stoves are a major cause of small particle pollution that damages our health and the environment. We look at the facts and advise on how to reduce the risks.
There’s no denying that wood burning stoves create a warm ambience in our homes. You can’t beat snuggling up when it’s chilly outside to the flickering and warmth of real flames.
But that welcoming glow comes at a cost. Wood burning stoves emit tiny, harmful, airborne pollutants that pass easily into our blood and lungs. They also contribute disproportionately to environmental pollution.
No surprises then that the government, as part of its 25-year environmental plan to improve air and water quality, is cracking down on emissions from wood burning stoves. New, stricter regulations on permitted emissions from domestic stoves now mean the amount of smoke a wood burner can emit from a chimney per hour falls from 5g to 3g.
Households in England with a wood burning stove face a penalty of £300 if they don’t comply, with fines reaching £1,000 for burning unauthorised fuels with higher emissions, unless using an “exempt” stove – designed to reduce emissions – from a list approved by the Department for the Environment, Food & Rural Affairs (Defra).
The rule applies to homes in “smoke control areas”, which includes most towns and cities in England. Defra has a map where you can check if your home is within a smoke control area.
According to the government, wood burning stoves and coal fires are the single largest source of a form of pollution called particulate matter 2.5 (PM2.5), which the World Health Organization (WHO) says is the most serious threat from air pollutants to human health.
These tiny PM2.5 particles can penetrate deep within our bodies, passing through our lungs and into our blood. From there they can move around the body and have been linked to a range of health problems, including heart failure, lung problems and dementia.
According to a study published by the University of Sheffieldwood burners flood rooms with these dangerous particulates each time the stove door is opened to put in more fuel. This simple action can double and even triple levels of PM2.5 inside homes, leading the study’s authors to advise that stoves should come with a health warning.
The WHO recommends that no one is exposed to more than 15 micrograms of PM2.5 per cubic metres of air (15ug/m3) on average over a 24-hour period. However, the Sheffield researchers found that people using stoves in their study had been exposed to over this amount, at between 27.34ug/m3 and 195.83ug/m3 on average while their stoves were lit. With those periods of use averaging four hours, this far exceeds the WHO’s recommendations.
Rohit Chakraborty, who led the Sheffield study along with Dr James Heydon from the University of Nottingham, said: “Our findings are a cause for concern. It is recommended that people living with those particularly susceptible to air pollution, such as children, the elderly and vulnerable, avoid wood burning stoves. Bursts of particulate matter can enter the home when the stove door is opened, flooding the inside space with air pollution during the refuelling.
"These particles are so small the body struggles to filter them out, making them harmful to children, the elderly and those with respiratory issues.”
And according to Professor Stephen Holgate, the Royal College of Physicians’ special adviser on air quality: “Inhaling combustion particles from any source is harmful, but more so than ever when it’s directly within your home.”
Keep the door closed
What if you already own a wood burner, or are thinking about getting one? The good news is there are things you can do to cut your exposure to harmful particles from your wood burning stove.
One obvious thing is to keep the door closed and minimise the time it is open for lighting or refuelling. Tom Edmunds, general manager at Wunda Group, an underfloor heating specialist, advises: “Only ever use the log burner when you need to, and once your home is warm, stop feeding the burner and focus on retaining heat.”
Since January 2022 all new stoves must meet the 2022 Ecodesign Regulations, which form part of the government’s Clean Air Strategy. So if you’re thinking of getting a wood burner, a new model is likely to be less polluting than a reclaimed model.
Andy Hill, chair of the Stove Industry Alliance, claims that Ecodesign technology produces 90% fewer emissions than an open fire, and 80% less than a typical 10-year-old stove. But Ecodesign wood burning stoves still produce 450 times more toxic air pollution than gas central heating, according to data published in the Chief Medical Officer’s Annual Report 2022.
These findings are echoed by Dr Brian Moench, chair of the board at US-based Doctors and Scientists Against Wood Smoke Pollution, who is not convinced that advanced technology makes newer wood burning stoves any less polluting.
“Even under the best circumstance, wood is always the most polluting way to heat a home and wood smoke is the most toxic type of pollution the average person ever inhales,” he says.
Fuel matters
Burning good quality fuels does make a difference. The moisture content of logs contributes to the level of pollution they create and affects efficiency: burning a wet log decreases efficiency as energy is needed to remove the moisture from the log before heat is released.
However, a completely dry log isn't ideal. According to HETAS, a non-profit biomass and fuel heating organisation, a moisture content of between 12% and 20% aids the combustion process and liberates the right amount of heat energy to the room. If wood is too dry, with a moisture content below 10%, it burns too fast, pulling in air that cools the flue gases and increases emissions.
Bruce Allen is CEO of HETAS and Woodsure, a woodfuel not-for-profit certification scheme. When buying solid fuel, he recommends looking for the Ready to Burn logo, which ensures the fuel is certified as having a moisture content of less than 20%. The logo will be accompanied by the manufacturer’s details and a certification number.
“When burned, wetter wood leads to five times more emissions than when Ready to Burn certified fuel is used,” Allen explains. “It is also important to check that your wood fuel is being stored correctly, so as not to compromise its integrity. Fuel should be kept off ground, with ample space and ventilation to avoid rotting.”
“It is also essential to perform regular maintenance by taking out any soot or ash and ensure that your chimney is clear. Try to stick to dry wood as opposed to wet wood where you can and look into purchasing sustainable firelighters which are free of fossil fuels and 100% carbon-neutral.”
It's worth having your chimney swept at least once a year. It can be a messy business and we'd recommend calling in a professional, who'll also supply you with a dated certificate to confirm it's been swept. It will also give your reassurance that they job has been completed properly, rather than attempting to clean your chimney yourself and potentially invalidating your insurance.
Domestic wood burning isn’t just a problem for people who have home wood burners. It made up 21% of PM2.5 emissions for the UK in 2021, an increase of 124% since 2011, according to government estimates.
To put that in perspective, domestic wood-burning is now producing more small particle pollution than road traffic.
The government estimates that around 1.5m UK households have wood burning stoves, with UK industry data showing stove sales running at between 150,000-200,000 per year.
The government says it has a clear framework for tackling air pollution to make it easier for local authorities to enforce the new regulation. But David Renard, commenting on behalf of the Local Government Association, said: “While the LGA supports new powers for councils to issue civil penalty notices, councils are facing significant funding challenges that will make monitoring and enforcing breaches of limits very challenging.
“It is important that people are given clear messaging about the health hazards to households and the neighbourhood. The Government also needs to work with a wide range of partners to take the action that removes the sources of air pollution everywhere, so that all communities have the benefits of clean air.”
Camden Council in London is one local authority that is taking control. It now requires all new wood burning appliances to be registered, in a bid to promote clean air. How each council operates will vary, so it’s worth contacting your local authority to check on its procedures.
The government has said it is tightening the rules rather than implementing a ban, as some households use wood burners for heating and cooking. The Stove Industry Alliance (SIA) says it is pleased that the government has not banned domestic burning.
“The SIA welcome the reduced emissions limits, as many modern stoves operate at levels better than those being set by the government,” said Hill.
“Where consumers are using the right appliance with the right fuel (less than 20% moisture) there will not be any issues regarding causing a nuisance and they should continue using, benefiting from and enjoying their wood burning stoves as much as they wish.”
