Emissions and air quality impacts from wood burning can be reduced with proper burning practices

Residents of the Helsinki metropolitan area already manage relatively well with low-emission wood burning, but there is still room for improvement, according to a report published by HSY. Using cleaner burning methods can improve your own and your family’s health and enhance local air quality. In addition, you can recover more energy from the wood, and your fireplace will stay in better condition.

Wood burning is common in the Helsinki region’s detached houses

Wood burning is widespread in detached house areas in the Helsinki region. In just over 70 percent of these homes, wood is burned - most often as supplementary heating - according to a report by Helsinki Region Environmental Services (HSY) on fireplace use and emissions. The most popular fireplaces are heat-retaining stoves and sauna heaters.

Wood burning produces emissions such as fine particles and PAH compounds, which impair air quality and are harmful to health. In the Helsinki region, wood burning generates more fine particle emissions than traffic exhaust.

“Wood burning worsens air quality most in densely populated detached house areas, especially on calm, frosty evenings. With proper burning techniques, emissions are significantly lower, heat is better utilized, and the fireplace stays in better condition,” says HSY air quality expert Nelli Kaski.

In the Helsinki region, wood burning causes the most emissions in Espoo, as most detached houses are located there. However, the average wood consumption per house is slightly higher in Vantaa than in Espoo and Kauniainen. In Helsinki, wood is burned less per house on average than in the other cities of the region.

Correct burning can significantly reduce emissions

Although many consider themselves experienced wood burners, low-emission burning techniques are not always mastered. Every wood burner can significantly influence the air quality of their living environment by burning correctly. In addition, new fireplaces are generally less polluting than older ones.

Harmful emissions occur especially when burning waste or wet wood. Poor burning practices produce many times more emissions compared to skillful burning of dry wood.

“Our report shows that some residents burn trash in their fireplaces. Burning trash produces large amounts of harmful emissions and also damages the fireplace,” Kaski says.

HSY’s report indicates that nearly 80 percent of residents who burn wood use dry firewood.

“An easy way to reduce emissions is to burn dry wood. Most people already do this. If possible, the best place to store wood is a ventilated woodshed, which keeps the wood dry,” Kaski says.

Smoke colour reveals the amount of emissions

The colour of the smoke coming from the chimney shows how clean the combustion is. The lighter, the better.

“If dark or acrid smoke comes from the chimney, emissions are high and combustion is not energy efficient. The reason may be too little combustion air or burning trash or overly moist wood,” Kaski says.

Kaski gives 7 tips for low-emission wood burning. Try these tips and see if the smoke becomes colourless:

1. Remove old ashes.
   
   
2. Burn only dry wood. Bring firewood indoors 1–2 days before use.
   
   
3. Do not burn trash.
   
   
4. Fill the firebox only halfway. Place larger logs at the bottom and smaller ones on top. Leave space on the sides.
   
   
5. Light from the top unless instructions say otherwise. Use wood-based kindling such as birch bark, chips, sticks, or ready-made wood-based fire starters.
   
   
6. Adjust the air supply. Combustion should not be too strong and roaring, nor too weak and smoldering.
   
   
7. Fireplace age and type matter. New fireplaces are often less polluting than old ones. For example, a heat-retaining stove with doors has better efficiency than an open fireplace and produces less emissions.

Wood burning produces various emissions

Wood burning generates health-damaging emissions: fine particles, carbon monoxide, black carbon, volatile organic compounds, and PAH compounds (polycyclic aromatic hydrocarbons), including benzo(a)pyrene. Many PAH compounds increase cancer risk. Long-term exposure has been shown to increase morbidity and premature mortality. Emissions also reduce the comfort of residential areas.

Wood consumption and fireplace usage data are based on a survey conducted in spring 2024, sent to over 4,000 detached house residents in the Helsinki region. About 1,600 responded. The data are compiled in HSY’s report “Fireplace use and emissions in the Helsinki region in 2023 (in Finnish).”

More information:

• Tips for cleaner wood burning: hsy.fi/burnwoodcleanly
• HSY report: Fireplace use and emissions in the Helsinki region in 2023 (in Finnish)