Study Shows 40% of Dangerous Wood Burning Stove Pollution From Sauna Stoves

An inconvenient truth: Wood burning saunas contribute to global warming and local pollution.  In Finland, around 40% of the fine particle emissions are from sauna use. There are easy ways reduce wood burning stove pollution and burn more efficiently.

The Helsinki environmental board has released alarming concerns about small particle emissions from wood burning saunas in Finland.  The difference in emissions between heaters is 100-fold, but the researchers are not yet releasing scorecards of manufacturers or particular heaters.

The research project called KIUAS, measured emissions from popular wood sauna stoves in real world conditions.

Where There’s Smoke There’s Wood Burning Stove Pollution

According to the researchers, the color of the smoke tells you everything you need to know about emissions and how to burn cleaner.  The goal is to achieve colorless smoke. If smoke is dark or brown, emissions are too high. Colorless smoke is less polluting and is far more efficient, saving a lot of firewood.

Each stove is unique in structure, operations, and emissions so you’ll have to experiment a bit.  Factors that contribute to a clean burn include:

  • Wood batch size
  • Pull conditions
  • Supply of combustion air
Wood burning stove pollution

Additional tips for achieving colorless, low-emission smoke:

  • Remove old ashes regularly.
  • Use dry wood, not wet or fresh.
  • Never burn any garbage.
  • Light up quickly. Use the driest wood to ignite. If necessary, you can use the ignition pieces to ignite.
  • Burn in several lots. Start with small trees. Add another bet until the flames fall.
  • Adjust the air under the grate and hatches.
  • Take care of regular scrubbing.
Watch the video to learn how to get cleaner sauna bath/löyly. It really matters how and what you burn in your sauna stove/kiuas. The emissions of wooden stove can be several times higher, depending how you burn wood. By observing the color of smoke you can find the most efficient way to use your stove. If the smoke is dark or brown, emissions are high. When the smoke is colorless, sauna pollutes less. When you use your stove in low-emission manner, it has a good importance to your health and your neighborhoods air quality.


Among other things, burning wood produces small particles and carcinogenic PAHs, or polycyclic aromatic hydrocarbons

Small Particles

These silicon particles are less than 2.5 microns in size. They consist of chemically different compounds such as polycyclic aromatic hydrocarbons, i.e. PAHs and soot. Small particles are considered particularly harmful to health, as they can penetrate deep into the airways.

Exposure to particulate matter in a residential area increases, for example, asthma and cardiac symptoms and, in the long term, also mortality. These emissions can multiply depending on combustions methods.

If burning wood inefficiently, particulate and PAH emissions are many times (up to 100x) higher than state-of-the-art combustion.

Regulations & Next Steps

Helsinki finland sauna innovation labThe stakes are especially high in the Helsinki metropolitan area, where 28% of the 70,000 houses use wood stoves.  Regulating the gasification of wood is a key issue, says Jarkko Tissari, a researcher at the University of Eastern Finland, who is surprised by study.

According to the Finnish Environment Institute, about half of Finland’s small particle emissions originate from household firing. The share of sauna heaters in the wood burning sauna stove pollution is unknown, but could be significant.

The KIUAS researchers hope the results can be utilized to work with manufacturers to develop less polluting sauna and water heaters.  They plan on launching a project to help develop next generation wood burning stoves and release a national eco-label to help customers purchase a low-emissions stove.

Right now, the consumer has no scientific way to know which stoves burn the cleanest, and there is no timeframe for making the KIUAS results public.

The growing project now includes the University of Eastern Finland, the Ministry of Environment, the Ministry of Social Affairs and Health, the Finnish Environment Institute, the Helsinki Region Environmental Services HSY and the cities of Helsinki, Turku, and Kuopio.

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