The Burning Question

Burning wood and coal in stoves and open fires is a large contributor to emissions of particulate matter in the UK and is a contributing factor in elevated concentrations of PM in the air towards the end of autumn and in winter months.

Air pollution is one of the biggest environmental risks to our health. When the tiny particles of PM are breathed in, they can contribute to serious health problems including strokes, asthma, heart disease and lung cancer. That's scary, so that is why we are doing it.

Particulate matter (PM) is everything in the air that is not a gas, and consists of a huge variety of chemical compounds and materials, some of which can be toxic.

Particulates are classified according to size: PM10 particles measure less than 10 micrometres in diameter, while PM2.5 particles are smaller than 2.5 micrometres.

Where does Particulate Matter come from?

Around half of the concentrations of PM that people in the UK are exposed to come from either naturally occurring sources, such as pollen, soil particles and sea spray, or are transported to the UK from international shipping and other countries.

The remaining PM in UK air results from human activities such as wood burning, various industrial processes and emissions from vehicles, mainly from tyre and brake wear. Secondary PM can also form in the atmosphere through changes in pollutants and reactions between them.

How does Particulate Matter harm our health?

The larger PM10 particles tend to get deposited in our nose and throat, but the smaller PM2.5 particles can get drawn deeper into the lungs. PM2.5 is so small that you can fit 28 of them across the width of a human hair.

Because their small size makes it easy to breathe them in, these particles move from our lungs into the bloodstream and can become embedded in our organs, increasing the risk of serious illnesses. The brain (strokes), heart and other organs can all be affected.

Exposure to PM can particularly impact the health of vulnerable groups of people such as the young, elderly, and those with respiratory problems.

By taking some simple steps to burn well, burn better or simply burn less often, we can improve the air we breathe at home and outside.

How much of a problem is burning at home?

In 2023, 20% of total PM2.5 emissions and 10 per cent of total PM10 emissions came from burning wood, solid smokeless fuels, coal and fuels derived from waste such as coffee logs.

Choose the right appliance and follow the guidance

1) Always use your open fire or stove in line with the manufacturer and installer’s guidance - find your nearest HETAS installer and retailer.

They can help you choose the right appliance for your space, and give advice on maintenance and using the correct fuel.

Burn the correct fuels

2) Only burn the correct fuels. The following give off harmful particles and toxic chemicals that will contribute to air pollution and should not be burned.

• Treated/painted/glued wood
• Old furniture
• DIY off cuts
• Household waste or plastic
• Turf
• Traditional house coal, also known as bituminous coal - this has been banned since 2023 under the Air Quality Regulations. Approved solid fuels are more efficient to burn and create less smoke - see a list of authorised and certified fuels that can be used
• Wet, recently cut or unseasoned wood - moisture creates smoke and harmful particulates when burnt. As well as being harmful to your health and the environment, this can damage your stove and chimney and is an inefficient way to heat your home, producing less heat

Store wet or unseasoned wood properly

3) Store wet or recently felled wood in a dry place where air can circulate for at least two years. Protect it from the weather to prevent it absorbing excessive amounts of rain water. Ensure your logs are stored off the ground and don’t stack them too tightly otherwise the air won’t be able to circulate properly. 

Even Ready to Burn wood can reabsorb moisture if it is not kept correctly. See advice on how to best store your firewood.

Use a moisture meter

4) Use a moisture meter to check the moisture content of the wood before burning. It should have 20% moisture or less. This video shows you how to use a moisture meter and to check for signs of dry wood without one.

If you haven't got a moisture meter, here is how to know your wood is dry enough to burn:

• Look for radial cracks and loose bark and a pale colour
• Dry wood should feel light in weight without the moisture
• If you knock two pieces of wood together and the sound is a dull thud, it is probably still too wet to burn
• Look for sustainably-sourced wood by checking it comes from a nearby managed woodland

Store ready-to-burn wood away from your stove or fire

5) Store dry wood away from the stove or fire. Storing it too close may cause it to catch fire. Find out about safely storing your wood indoors.

Use a professional

6) Make sure your open fire or stove is installed by a registered/certified installer - find a log burner and wood burning stove installer.

Service your stove and sweep your chimney or stove pipe at least once a year.

Use a stove thermometer and a stove fan

7) A stove thermometer indicates the optimum burn range to ensure you get the most heat from your fuel, use less wood and extend the life of your appliance.

It shows when the stove gets too hot so you can reduce the air supply to reduce the temperature. It also shows when you are burning at a temperature that’s too low. This leads to inefficient combustion, which in turn produces more smoke, tar and creosote which can block the flue pipe and is a major cause of chimney fires.

A stove fan sits on top of your stove. Once the stove reaches a good operating temperature, the fan will help to circulate the hot air rising from the stove and distribute the heat more evenly. That means you may need less fuel to feel warm.  

Check your ventilation system and carbon-monoxide detector

8) Make sure that the ventilation system of your wood stove is clean, and has no blockages in order to prevent carbon-monoxide building up.

Make sure a carbon-monoxide detector is fitted and working. Do not cover it up or move its location. 

Ventilate your home to clear the air

9) Periodically opening windows or doors, helps fresh air move the pollutants from inside to outside. Consider using an air purifier to help filter-out particles.

Light your fire correctly

10) Know how to light your fire correctly. Do this by checking the manufacturer’s instructions, speaking with your local chimney sweep or follow this advice from HETAS on how to light your fire.

Keep the stove door shut unless you are refuelling

11) Don’t leave the stove door open. This wastes heat, increases harmful emissions and increases the risk of accidental fire. Unless you are refuelling, keep it closed.

Reduce puffs of smoke entering the room when refuelling

12) Refuel when the fire is down to glowing embers, not flames.

When refuelling, open the stove door a little, then pause to allow the pressure to adjust. Then open the door slowly and gently to put more fuel on. This will prevent a rush of smoke in the room which happens because of a pressure difference or a drop in the chimney’s draft.

Don’t slumber your fire overnight

13) Slumbering is where your appliance is set at minimal output, usually overnight, so that burning can be resumed without needing to relight a fire. Running an appliance at low output can lead to incomplete combustion when burning wood, leading to a build-up of creosote deposits in the flue, as well as increased levels of carbon monoxide and particulates

Don’t overload your fire

14) Don’t overload your stove – too much fuel can smother the fire and prevent a clean burn. 

Don’t let the ash pile up

15) A little ash can help get your fire going; too much and it can be dangerous and affect the amount of heat your stove produces. 

Use the air controls properly

16) Use your air controls properly. Don’t close the air control fully as this will starve the fire of oxygen and affect the quality of the burn. Keep a steady controlled burn and don’t burn too hot as this can damage your appliance.

Check for smoke coming out of your chimney

17) When you first light your stove, the fire is cool. This is the only time you should see smoke coming from your chimney. Once it has been burning for about 15 minutes, check your chimney again for smoke. If you see smoke coming from your chimney, there is not enough air getting into the stove. Open the controls up and allow the fire to build then check again.

If you can’t see smoke, you’ve got it right. 

Watch this YouTube video to assist:

Get your chimney swept each year by a professional

18) Regular sweeping allows free passage of combustible gasses. It will remove soot, bird nests, cobwebs and any other blockages, as well as creosote, which helps to prevent dangerous chimney fires.

Don’t forget to ask your chimney sweep for your certificate of chimney sweeping – you’ll need this as a record of sweeping, and for fire safety and insurance purposes.

Where is the best place to find a local chimney sweep?

• The Federation of British Chimney Sweeps
• HETAS
• Sweep Safe, The UK Chimney Sweep Association

We spend up to 90% of our time indoors. Indoor and outdoor pollution are closely linked through the movement of air, shared pollutants, and the creation of outdoor pollution from indoor sources. Outdoor air enters buildings through ventilation, and outdoor pollutants can then become trapped and concentrated indoors.

Conversely, indoor activities like cooking and the burning of fuels release pollutants that can negatively impact outdoor air quality.

Indoor sources, such as cooking, gas stoves, candles and incense release pollutants including PM and Volatile Organic Compounds (VOCs) when they burn.

Cosmetics and cleaning products can also release PM and VOCs. Asthma + Lung UK talk about the sources of indoor pollution and how to improve the air quality in your home.

The Met Office provides an air quality forecast for DEFRA based on five key pollutants - ozone, nitrogen dioxide, sulphur dioxide, PM2.5 and PM10 particles.

The Daily Air Quality Index (DAQI) tells you about levels of pollution and also provides recommended actions and health advice you may wish to take according to the level of air pollution. The Index is numbered from 1 (low pollution levels) to 10 (high pollution levels).

View the air pollution in your area online by simply entering your postcode.