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22 October 2020

Stoves and pollution

Considering a stove but concerned about pollution? Our guide looks at the pollution a stove can create and how to minimise it, so you can make an informed decision.
Chimney smoke from a wood burning stove 472173
Liz Ransome-Croker

There has been a lot of coverage in the media about potentially harmful pollutants from stoves. Pollutants are generated from a range of things we encounter in our daily lives – from cars on busy streets, to heating and cooking appliances in our own homes. 

So should you still use a stove? We explore the kind of pollution a stove can produce and how you can minimise it. 

If you're worried about the effects of stoves on pollution, you might want to consider a gas or electric stove as an alternative.

Is a wood-burning stove bad for the environment?

According to the Department for Environment, Food and Rural Affairs (Defra), while UK air quality has improved significantly over the past few decades, the burning of solid fuels (such as coal and wood) in our homes is the largest contributor of harmful particulate-matter (PM) emissions.

Its Clean Air Strategy (published January 2019) states that this makes up 38% of our national PM emissions while, in comparison, industrial combustion is 16% and road transport 12%. 

It's worth nothing that within this figure is the use of open fires and 'dirtier' fuels, such as wet logs and house coal, both of which emit higher levels of PM.

In addition, separate research released in January 2020 indicates that the 38% might also include other types of unregulated burning as well, such as pizza ovens and bonfires.

Commissioned by Heating Equipment Testing and Approvals Scheme (Hetas), which tests and approves fuel, stoves and installers, and the stove manufacturers' organisation Stove Industry Alliance, the report also indicates that the predictions around the amount of fuel burnt is overestimated and that not the most accurate methods of measuring PM levels were used.

Is there going to be a wood-burning stove ban?

The government is not going to ban stoves, but instead educate consumers and introduce measures that will make sure people burn cleaner fuels and that stoves emit fewer pollutants. 

Limit the sale of polluting fuels

As mentioned above, wet logs and house coal produce far more particulate matter than dry logs and low-sulphur solid fuel, such as anthracite coal.

The government is bringing into force legislation that will mean only the more efficient fuels will be on sale. This will include banning the sale of small amounts of wet wood with higher than 20% moisture content by February 2021. 

Large batches will still be available to buy to be seasoned at home (which means being left to dry, a cheaper way to buy fuel for your stove), but advice must be given with them.

Also, from February 2021 the sale of pre-packaged bituminous house coal, which produces high levels of sulphur as well as particulates, will be banned. It will still be sold loose, but only until February 2023. There is already a limit in Smoke Control Areas on burning fuel containing more than 2% of sulphur. 

In addition, the government will push for innovations with developing and producing less-polluting fuels and is working with industry, including Hetas, the Stove Industry Alliance and chimney sweep organisations, to educate consumers at the point of sale or when having their chimney swept or maintained.

Only the 'cleanest' stoves on sale 

By 2022, the EU has stipulated that all stoves must meet higher efficiency levels and new maximum emission limits (visit our page on buying a wood-burning stove to find out more). The government will work with industry to ensure that this target is met and that appliances are tested in the right way.

You can find out more below about ways to minimise the effects of stove pollution, including using the right fuels and having an efficient stove. You might also want to look at getting a gas or electric stove instead.

Update legislation around Smoke Control Areas 

According to councils, rules around Smoke Control Areas, such as only burning certain types of fuel, are adhered to with varying degrees – scroll down below to find out more about Smoke Control Areas. 

The government is working with local authorities and retailers to raise awareness of these rules when a stove is purchased. 

It will also make changes to the Environment Bill to ensure smoke-control legislation is easier for local authorities to enforce and look to give authorities more power around reducing pollution further in their area.

Should I still get a stove?

Cooking, cleaning and heating appliances, including stoves, all produce pollutants. 'Dirtier' fuels and inefficient and non-Defra-exempt stoves will be much worse, so you should steer clear of these.

Many of the pollutants are only a problem if you're exposed to high levels over a long period. These problems are likely to be more noticeable in individuals with pre-existing respiratory conditions. But they will also contribute to overall levels of pollution nationally.

Our section on types of pollution and the results from our air pollution investigation tells you more about the different types, where they come from, the effects they can have and how you can minimise potential problems. 

Not having a stove will, of course, mean fewer pollutants. But stoves do have some good points, especially when it comes to carbon emissions.

Biomass materials, such as wood, are considered a low-carbon source of energy as they absorb carbon while growing. 

Locally produced biomass materials are even better in terms of carbon, as less is produced when transporting them across shorter distances. This can also help you to save money.

There are also things you can do to make sure your stove isn't producing more pollutants than it should – keep reading for six ways to minimise the effects of stove pollution.

If you're really concerned about pollution, or have severe health conditions (especially respiratory related), a stove might not be the best option for you.

If you're still want to have the same the look and feel of a stove, a gas or electric version could be a good option.

You might also want to also consider getting an air purifier to combat pollution. Our tests reveal the ones that can truly be trusted to quickly and effectively clean the air in your home – find out which are the best air purifiers.

Six ways to minimise the effects of stove pollution

From burning the right fuel to making sure you maintain your appliance, you can minimise pollutants from stoves.

1. Buy an efficient stove

Although new rules for minimum efficiently levels (called Ecodesign) won't come into force until 2022, the Stove Industry Alliance (SIA) is working with manufacturers to create stoves that meet the emissions part of the criterion now (not the entire criteria).

Named Ecodesign stoves, these models should produce fewer harmful gases. The SIA says they reduce potentially harmful particle emissions by more than 80% compared with stoves made 10 years ago. Stoves that fulfil these requirements will be labelled ‘Ecodesign Ready’.

You can visit the Hetas website to find out more about the Ecodesign legislation that will become a legal requirement for all stoves in 2022. 

Go to how to buy a multi-fuel stove or log burner for more information on what you need to consider when buying a stove - including efficiency, wattage and building regulations.

2. Get a Defra-exempt stove to burn wood

If you live in a smoke-controlled area, you'll only be allowed to burn smokeless fuel – such as anthracite coal. If you want to burn wood, you'll have to buy a Defra-exempt stove (also called Defra-approved).

Even if you don't live in one of these designated areas, a Defra-exempt stove could be a good option to help cut emissions. This is because these stoves fit government criteria for emission levels and the amount of smoke they produce. 

Wood creates more smoke if it doesn't have a good enough supply of oxygen. Defra-exempt stoves make it harder for wood to smoulder and stop it from ever being completely starved of oxygen. So, as well as reducing emissions, it will minimise soot build-up in your chimney. This will keep your flue clearer for gasses to escape.

We'd recommend getting a stove that is both Defra-exempt and complies with Ecodesign criteria. Our wood-burning stove review pages detail whether companies sell these types of stoves. You can also check this on the Defra website and Hetas website.

3. Don't use wet logs on your stove

To help reduce potentially harmful emissions from your stove, only burn wood with 20% or less moisture content. It will also minimise sooty deposits building up in your chimney, which can be a fire hazard. 

Dry wood is also more efficient, as energy won’t be wasted having to burn off the water first, so the heat output will be higher. 

Kiln-dried logs should have 20% or less moisture – 35% of the Which? members we surveyed* use these most regularly – or you can dry out wetter logs yourself. This is called seasoning and is what most people use (81%). 

Keep in mind that seasoning could take two or more years, depending on how wet the wood is to begin with and the conditions you store it in. You can buy a moisture meter to check the levels.

If you’re buying wood, as opposed to drying it yourself, look out for the Woodsure Ready to Burn logo. This new government-backed scheme means that only wood from reputable manufacturers can display the logo on logs that do contain less than 20% moisture.

Also make sure you never burn treated wood, such as from an old piece of furniture, as it could let off toxic chemicals.

Our advice on using a log burner or multi-fuel stove tells you more about the different types of fuel, using them efficiently and the Ready to Burn logo.

4. Burn smokeless fuel instead of house coal

Burning smokeless coal is more environmentally friendly than using house coal, as it produces fewer emissions. Some 22% of stove owners that answered our survey use this regularly and only 4% use house coal. 

Smokeless coal is an umbrella term for a few different types of coal that produce less smoke as they burn. It includes anthracite coal – this occurs naturally, but can also be manufactured.

Man-made smokeless coals can contain a combination of elements, including anthracite and other renewable materials, making many of them more eco-friendly than house coal.

Look for smokeless fuel with 2% or less sulphur, as high levels of sulphur can impact your health, and damage stoves and chimneys. 

For smoke-controlled areas, the Clean Air Act 1993 stipulates that smokeless solid fuels mustn't contain more than 2% sulphur. The government will extend this to apply the rule nationally.

5. Learn to keep your stove burning well

Wood that doesn't have a good supply of air is likely to smoke more, therefore producing higher levels of potentially harmful emissions.

Whether you're burning wood or smokeless fuel, leave the door ajar and open air vents while you're getting the fire going. Once established, use the air vents to keep the fire burning.

Ensure the flue stays at the right temperature throughout use by making sure the fire is constant. Building burning materials into a teepee shape at the beginning will help. 

This will help avoid carbon monoxide – an odourless and potentially deadly gas – coming down the chimney. 

It's worth buying a stove thermometer to monitor the temperature. Most stoves should stay between 200°C and 250°C. This can vary for each stove, so check with your manufacturer.

Go to using a log burner to watch our video on the best way to light a wood fire.

6. Clean and maintain your stove regularly

Having your chimney swept regularly is vital for ensuring it doesn't get overloaded with sooty deposits. Any obstructions could become a fire hazard and will prevent smoke from escaping properly.

You should get it swept quarterly while it's in use if you burn wood or coal. If you burn smokeless coal, you should get it swept yearly. 

Worryingly, 4% of people we spoke to never get their stove swept. However, a high proportion (59%) get it swept annually and 31% every few years.

You can find a chimney sweep on sites such as the National Association of Chimney Sweeps, Hetas or Which? Trusted Traders, where we vet traders before awarding them a Which? logo.

Make sure you also examine your stove for any cracks, distortions or other problems and get them checked by a stove installer or chimney sweep.

Any faults could mean harmful pollutants are making their way into your home.

Types of pollution in your home

There are three main types of pollution in our homes: particulate matter (PM), gasses and volatile organic compounds (VOCs).

1. Particulate matter

Combustion is created by wood and coal fires, but also by regular activities - such as burning candles, using electric toasters and gas cooking. Combustion produces tiny particulate matter. This can also come from dusting and vacuuming. 

Particulate matter can inflame your airways and increase the risk of lung and heart disease if inhaled at persistently high levels over time.

2. Gases

Gases – including carbon dioxide (CO2), nitrogen dioxide (NO2) and carbon monoxide (CO) – are emitted by appliances that burn fuel, such as open fires, gas cookers and gas boilers.

  • CO2 is produced by human respiration and burners operating normally. High levels of CO2 over time, which can come from poor ventilation, can result in drowsiness, impaired thinking, dizziness and headaches. Individuals with lung disease and impaired lung function could be particularly affected. 
  • NO2 is produced by combustion. In homes with gas stoves, kerosene heaters or unvented gas-space heaters, indoor levels often exceed outdoor levels, possibly increasing the effects of exposure to allergens, such as house dust mites, and irritating the eyes, nose, throat and respiratory tract.
  • CO is produced when carbon-containing fuel burns without adequate oxygen. For example, by poorly maintained gas heaters and boilers, portable gas or paraffin heaters with no flue and badly installed stoves.

CO is an odourless, but potentially deadly, gas. Every home should have at least one working carbon monoxide detector, correctly positioned. But don't think every carbon monoxide detector is up to the job of protecting you and your family. 

Our tests have uncovered carbon monoxide alarms that can't be relied upon to detect the gas and sound the alarm. Discover our Don't Buy carbon monoxide detectors.

3. Volatile organic compounds

Volatile organic compounds (VOCs) are chemicals found in a wide variety of materials. They're produced when cooking and using heating appliances, such as wood burners and non-electric space heaters. VOCs evaporate into the air at room temperature, forming vapours that we breathe. 

Different classes of VOCs have different risk levels. For example, benzene (from petrol and cigarette smoke and, potentially, from paints and solvents) is high risk. Whereas terpenes, including limonene and pinene (familiar lemon and pine smells used in scented toiletries and bathroom cleaners), are considered lower risk. 

VOCs can react with ozone from outdoor air, particularly in hot weather, to form the gas formaldehyde and other irritants. Formaldehyde is a lung irritant that can cause allergic reactions and, at very high levels, is carcinogenic. Formaldehyde can also be released from new flat-pack furniture, lino and carpet, fabrics, bedding, glues and insulation. 

Exposure to very high levels of VOCs can cause symptoms such as eye, nose and throat irritation, headaches and nausea and, in the long term, even damage the liver, kidneys and central nervous system. 

Our investigation into air pollution in the home

In December 2016, we took snapshot measurements of air-quality and ventilation rates in three semi-detached houses:

  • ‘draughty’ Victorian house 
  • 1950's house with many insulating improvements
  • new-build end-of-terrace. 

Our measurements were taken with the windows closed before, and almost immediately after, concentrated bursts of common household activities. This included vacuuming, cleaning, cooking and using personal care and scented products. 

We discovered surprisingly high levels of pollutants with potential cumulative long-term health effects in all of our test houses.

While the activities we performed were relatively short-term – making a fry-up, cleaning the bath and vacuuming – it’s the prolonged exposure to the generated pollutants that could cause health problems. 

It's important to stress that some people are more susceptible to the effects of indoor pollutants – for example, if you suffer from asthma, are sensitive to allergens indoors, or have heart aor lung disease. 

We're not suggesting you should worry about every candle you light, or open all the windows, even in winter. Our discoveries are more about potential cumulative effects over the longer term. But there are certain things you can do to limit the risks:

  • choose products that will minimise indoor pollution;
  • maximise ventilation by opening windows and trickle vents;
  • use bathroom and kitchen extractor fans.

Read our full guide on how to improve your indoor air quality at home

*January 2019 survey of 1,434 Which? members who have bought a stove in the past 10 years.