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How to behave in a smog situation

12. 02. 2021 Ovzdušie

In the event of a short-term but extreme deterioration of air quality, the Slovak Hydrometeorological Institute declares the so-called smog situation. When does it happen, how do you find out about it and what to do in case of a smog situation?


At the beginning of the year, the Czech Hydrometeorological Institute informed about the historically first year (2020) without the emergence of smog situations in the Czech Republic. Unfortunately, we cannot say the same in Slovakia. In 2020, we did not avoid smog situations, and we have already observed some smog situations in 2021. 

When does a smog situation occur?

A smog situation occurs when the level of air pollution of PM10, sulfur dioxide (SO2), nitrogen dioxide (NO2) or ground-level ozone exceeds the threshold value for any of the listed pollutants. 

Smog situations most often occur in the winter months due to emissions from domestic heating and transport. The situation is also aggravated by unfavorable dispersion conditions, temperature inversions. Mountain valleys and basins are the areas with the strongest and longest inversions, and at the same time there is a high contribution of solid fuel heating.

In the summer months, there is a risk of smog situations caused by increased concentrations of ground-level ozone, which is formed by the chemical reaction of nitrogen oxides and volatile organic compounds under the influence of sunlight.

How do I find out about a smog situation?

The smog warning system serves to warn the population against the adverse effects of polluted air during smog situations. According to the Air Act the Slovak Hydrometeorological Institute is obliged to issue a notification within 4 hours of identifying the smog situation. They are obliged to immediately inform the affected municipalities (web, information board, local radio) and public media (television and radio) about the occurrance of the smog situation.

You can also follow information about smog situations at

What to do in case of a smog situation?

In connection with smog situations, the emphasis is mainly on sensitive groups of the population - children, pregnant women, the elderly, chronically ill people, asthmatics. However, in the event of a smog situation, active people and athletes, should also pay attention to outdoor activities. In general, it is recommended to limit the physically strenuous activities outside, not to ventilate the area during the smog situation, and to seek medical attention when first signs of respiratory disease occur.