Air quality in Slovakia: where to check and what to do

Short answer. Slovakia's hydrometeorological institute, SHMÚ, publishes an air quality index (IKO) for each monitoring station in three levels: good (green), worsened (orange) and bad (red) ¹. Its smog warning system announces a smog situation when ozone passes 180 µg/m³ in one hour or PM10 passes 100 µg/m³ over 12 hours, and issues a warning at 240 and 150 µg/m³ ⁶.

Where can I check air quality right now?

On SHMÚ's air quality index page, which rates the current air at each station of the national monitoring network ¹. The same institute runs the smog warning system and posts the current status, with an archive ². SHMÚ's smog page also links to the European Environment Agency's index for other European countries ².

What do the index levels mean?

The IKO is calculated from hourly average concentrations of PM10, PM2.5, nitrogen oxides, sulphur dioxide and ozone at automatic stations; the worst pollutant sets the level ¹.

See Air quality index explained.

How polluted is the air on average?

The population-weighted median of Slovak cities shows about 13 µg/m³ of PM2.5 (annual mean 2021-2023) ³, more than twice the WHO guideline of 5 µg/m³ ⁵. Nitrogen dioxide is about 10.1 µg/m³ ⁴, just above the WHO guideline of 10 µg/m³ ⁵. That NO2 figure is a regional background over roughly 80 km: a busy street will be higher.

When are smog warnings issued?

SHMÚ's smog warning system covers ozone, PM10, NO2 and SO2 ⁶:

In the warning system's display, yellow means an hourly or daily limit value has been exceeded; it does not necessarily mean the yearly number of allowed exceedances has been used up ². For PM10, a daily mean above 50 µg/m³ is allowed on at most 35 days a year ².

What should I do on a bad air day, or with smoke or dust?

• Orange or red index: follow the official advice in the table above; people who are older, ill, pregnant or with small children should cut strenuous outdoor effort first ¹.
• Smog situation or warning: check SHMÚ's current status ² and how warnings reach you on our Slovakia alerts page. See Pollution episodes and Ozone days.
• Smoke or dust: Phaenyx found no official Slovak guidance on wildfire smoke. See Wildfire smoke, A clean-air room at home, Masks for smoke and Dust storms.

A household plan can note who at home is sensitive to polluted air and where to stay on bad days.

Frequently asked questions

Does Slovakia have its own air quality index?

Yes. SHMÚ's IKO rates air at each station in three levels, from good to bad ¹.

What ozone level triggers a smog warning?

180 µg/m³ as a 1-hour mean starts a smog situation; 240 µg/m³ for three hours in a row triggers a warning ⁶.

Who should be most careful?

Older and ill people, pregnant women and small children, according to SHMÚ's advice ¹.

Does a yellow mark mean a smog warning?

Not by itself. Yellow shows that an hourly or daily limit value was exceeded at a station; smog situations and warnings are a separate mechanism with their own thresholds ².

Sources

1. Slovenský hydrometeorologický ústav (SHMÚ) — Index kvality ovzdušia — https://www.shmu.sk/sk/?page=1&id=oko_iko (accessed 2026-10-27)
2. Slovenský hydrometeorologický ústav (SHMÚ), Riadiace stredisko smogového varovného systému — Smogový varovný systém — https://www.shmu.sk/sk/?page=1&id=oko_varovny_system (accessed 2026-10-27)
3. Atmospheric Composition Analysis Group (ACAG), Washington University in St. Louis — Surface PM2.5, V6.GL.02.04 (annual mean 2021-2023) — https://sites.wustl.edu/acag/datasets/surface-pm2-5/ (accessed 2026-10-27)
4. Copernicus Atmosphere Monitoring Service (CAMS) — CAMS global reanalysis (EAC4) — https://ads.atmosphere.copernicus.eu/ (accessed 2026-10-27)
5. World Health Organization (WHO) — WHO global air quality guidelines (2021) — https://www.who.int/publications/i/item/9789240034228 (accessed 2026-10-27)
6. Slovenský hydrometeorologický ústav (SHMÚ) — Časté otázky (kvalita ovzdušia, smogová situácia) — https://www.shmu.sk/sk/?page=1&id=oko_faq (accessed 2026-10-27)