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Pollution from local heating plants is a serious air quality problem and is a frequent cause of smog situations in the winter. The largest share of emissions of dust particles, but also of carcinogenic benzo(a)pyrene, comes from the burning of solid fuels in households. The problem of pollution from local heating plants is obvious in the countryside. This is evidenced by villages shrouded in thick smoke in winter, which have exceptionally good air quality outside the heating season. The situation in the winter is also worsened by poor dispersion conditions. Pollution is more dangerous when heating is done with unsuitable fuels - coal, wet wood, or waste (paper, plastics, furniture boards, etc.). In this case, in addition to a large amount of ultrafine particles, harmful chemicals can also escape into the air.

The OZ CEPTA measurements were carried out with the P-Trak Ultrafine Particle Counter from TSI, model 8525, which measures UFP with a diameter of 0.02 - 1 µm as the number of particles per 1 cm3 of air and clearly confirmed that heating with solid fuels significantly worsens air quality.

Heating season and inversions

In the villages of Gemerská Poloma and Dobšiná, Rožňava district, UFP measurements were carried out in the early evening hours, when most family houses were heating. The weather was stable, the inversion character and calm prevented the dispersion of pollutants. Pollution from heating was obvious at first glance - within the village of Gemerská Poloma, which is classified as risky with level 3 due to the risk of adverse air quality, a layer of smoke was floating.

The measured values exceeded 20,000 particles per cm3 of air, which is a concentration (hourly average) that the World Health Organization (WHO) considers a health risk.

The situation was very similar in Dobšiná. Inversion cold, windless weather prevailed and since it was Saturday evening, intensive heating was used in family houses. The air was extremely polluted, especially at the lower end of the village.

In the Banská Štiavnica district, UFP concentrations were measured in the villages of Kozelník and Banská Belá. The village of Kozelník is a small village in a narrow valley. Family houses are heated almost exclusively with wood. Many houses were heated in the afternoon and early evening hours, and a layer of smoke was formed over the village. Again, the value of 20,000 particles per cm3 of air was exceeded in several places. For comparison, clean air was also measured, excluding smoke from local fireplaces.

In the village of Banská Belá, the team measured very similar pollution to that in Kozelník. UFP pollution was also significant in Banská Štiavnica, in the development of family houses that are heated mainly with wood.

Emissions from heating in indoor air

Heating with solid fuels poses a risk not only to the ambient air. The measurements show that if there is a stove or fireplace in the interior of the house, there can also be very strong pollution of the indoor air in the house, especially if part of the smoke escapes into the interior, for example when adding wood. If the house is insufficiently ventilated, its residents are exposed to high concentrations of harmful ultrafine particles for a long time.

How to reduce harmful emissions of ultrafine particles from local heating?

• Use only dry wood for heating, do not burn waste or wet wood, follow the principles of proper heating,

• use modern heating devices with a low emission factor for heating,

• insulate the house well, which will significantly reduce the need for heating,

• use non-combustion heating methods such as solar collectors, heat pumps, optimally in combination with photovoltaics.

Ultrafine dust particles

Ultrafine dust particles are particles with a diameter of less than or equal to 100 nm (0.1 µm), which easily penetrate from the respiratory system into the bloodstream and can be transmitted to sensitive organs or the central nervous system. Their presence in the blood can affect its functions and properties. They are highly reactive and may contain heavy metals and toxic substances. The mass of UFP is negligible in the standard measured size spectrum of PM10 and PM2.5, therefore, measuring the number of particles and their size distribution is more suitable for assessing health impacts.

Compared to PM10 and PM2.5 particles, which are subject to regulation and have clearly defined measurement standards, UFP are currently not included in the national legislation governing air quality in Slovakia. The new EU Directive on Ambient Air Quality and Cleaner Air for Europe from October 2024 lists UFP as new pollutants that will be mandatory to monitor. Due to the size and population of the Member States, the requirements for the location of sampling points for measuring UFP vary.

Air quality assessment

The air we breathe is affected by emissions from industry, transport, households and other, including natural, sources, but also by dispersion conditions, whether meteorological elements or orography. Sampling devices of the national air quality monitoring network, operated by the Slovak Hydrometeorological Institute (SHMÚ), are, according to Decree No. 250/2023 Coll. on air quality, located 1.5 (breathing zone) to 4 meters above the ground. Pollutants have their limit or target values for the protection of human health and some of them also have a set number of permitted exceedances. Air quality assessment is carried out by the SHMÚ by determining the level of air pollution using methods of continuous measurement, calculation (modeling), prediction or estimation. The conclusions of the air quality assessment are published annually in the air quality report.

The Civic Association Center for Sustainable Alternatives (CEPTA) was established in 2005 with the aim of supporting and implementing activities that develop the principles of sustainability. As part of the LIFE IP – Improving Air Quality project, it measures ultrafine particles in the air in order to raise public awareness about the negative impact of air pollution on human health and present measures to reduce air pollution.

The report on measurements of air pollution by ultrafine particles from transport is available at: https://cepta.sk/wp-content/uploads/2025/02/Report-250228-Kureniska-SK.pdf