Short answer. Check the Czech Hydrometeorological Institute's (ČHMÚ) Air Quality Index (IKO), shown as a live map and table for each monitoring site 1. It has three traffic-light grades: green (very good to good), orange (acceptable, limiting outdoor activity is already recommended) and red (worsened to bad, outdoor activity not recommended) 1. Smog situations are announced through the ČHMÚ's Smog Warning and Regulation System (SVRS) 3.
Where can I check air quality right now?
On the ČHMÚ's index page, which links to the current IKO map and table 1. The index uses 3-hour rolling concentrations of sulphur dioxide, nitrogen dioxide and PM10 particles, plus ground-level ozone from 1 April to 30 September 1. It is calculated from current measurements that have not yet been verified 1.
Smog situations, regulations and warnings are published on the ČHMÚ's SVRS page, which the institute runs on behalf of the Ministry of the Environment, with a history since 2010 3. The SVRS covers PM10, sulphur dioxide, nitrogen dioxide and ground-level ozone 3.
What do the index levels mean?
Each of the three grades is split into two sub-grades, from 1A to 3B, according to the effect on sensitive groups 1. The SZÚ's advice for each sub-grade 2:
| Grade | Sensitive groups | General population |
|---|---|---|
| 1A-1B (very good to good) | Ideal conditions; outdoor activity without limits | Same |
| 2A (acceptable) | No need to change usual outdoor activity unless you notice symptoms such as cough or throat irritation | No limits |
| 2B (acceptable) | Consider reducing or postponing strenuous outdoor activity, especially if symptoms appear | No need to change usual outdoor activity |
| 3A (worsened to bad) | Limit strenuous activity, especially outdoors; asthmatics may need their reliever more often; all older people and children should limit physical activity | Consider reducing or postponing strenuous outdoor activity if symptoms appear |
| 3B (worsened to bad) | Shorten time outdoors and avoid physical effort | Limit or postpone strenuous outdoor activity, especially with any discomfort |
See Air quality index explained.
How polluted is the air on average?
Above WHO guidelines. The population-weighted median of Czech cities shows about 13 µg/m³ of PM2.5 (annual mean 2021-2023) 5, more than twice the WHO guideline of 5 µg/m³ 7. Nitrogen dioxide is about 12.7 µg/m³ 6, above the WHO guideline of 10 µg/m³ 7. That NO2 figure is a regional background over roughly 80 km: a busy street will be higher.
What should I do during a smog situation, or with smoke or dust?
The SZÚ's advice is aimed mainly at sensitive groups: children (including infants and the unborn child), older people, and people with chronic respiratory or circulatory disease 4. It recommends 4:
- limit time outdoors, especially between 6 and 10 am and between 4 and 8 pm;
- avoid heavy physical effort outdoors, such as physical work or sport;
- air rooms briefly and intensively, a few minutes 3-4 times a day;
- do not use fireplaces or burn anything outdoors, and never burn waste in stoves or boilers;
- start treatment early at the first signs of respiratory illness.
See Pollution episodes, Sensitive people and polluted air and Children and polluted air. For smoke, see Wildfire smoke, A clean-air room at home and Masks for smoke; for dust, Dust storms. A household plan can note who at home is sensitive to polluted air.
Frequently asked questions
Who announces a smog situation?
The ČHMÚ, which runs the SVRS on behalf of the Ministry of the Environment under the Air Protection Act (201/2012 Sb.) 3. For PM10, sulphur dioxide and nitrogen dioxide, the threshold must be exceeded at half or more of the representative stations, with a 24-hour outlook; for ozone, one station is enough 3.
Does the index include PM2.5?
No. The IKO is based on sulphur dioxide, nitrogen dioxide, PM10 and, in summer, ozone 1.
Who counts as sensitive?
Children, pregnant women, older people, people with asthma, chronic obstructive pulmonary disease or heart and circulatory disease, and people weakened in other ways 4.
Sources
- Český hydrometeorologický ústav (ČHMÚ) — Index kvality ovzduší — https://www.chmi.cz/cs/kvalita-ovzdusi/imise-informacni-system-hodnoceni-kvality-ovzdusi/podklady-pro-hodnoceni-ko/hodnoceni-ko-index-kvality-ovzdusi (accessed 2026-10-27)
- Státní zdravotní ústav (SZÚ), published by ČHMÚ — Doporučení SZÚ ke snížení expozice znečišťujícím látkám a ochraně zdraví — https://www.chmi.cz/documents/d/chmi.cz/szu_doporuceni-ke-snizeni-expozice-znecistujicicm-latkam-a-ochrane-zdravi?download=true (accessed 2026-10-27)
- Český hydrometeorologický ústav (ČHMÚ) — Smogový varovný a regulační systém (SVRS) — https://www.chmi.cz/kvalita-ovzdusi/smogovy-varovny-a-regulacni-system-svrs (accessed 2026-10-27)
- Státní zdravotní ústav (SZÚ) — Smogová situace – co můžeme udělat? — https://szu.gov.cz/temata-zdravi-a-bezpecnosti/zivotni-prostredi/ovzdusi/venkovni-ovzdusi/smogova-situace-co-muzeme-udelat/ (accessed 2026-10-27)
- 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)
- Copernicus Atmosphere Monitoring Service (CAMS) — CAMS global reanalysis (EAC4) — https://ads.atmosphere.copernicus.eu/ (accessed 2026-10-27)
- World Health Organization (WHO) — WHO global air quality guidelines (2021) — https://www.who.int/publications/i/item/9789240034228 (accessed 2026-10-27)
Turn this into action
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Sources
- Český hydrometeorologický ústav (ČHMÚ) · Index kvality ovzduší checked 2026-10-27
- Státní zdravotní ústav (SZÚ), published by ČHMÚ · Doporučení SZÚ ke snížení expozice znečišťujícím látkám a ochraně zdraví checked 2026-10-27
- Český hydrometeorologický ústav (ČHMÚ) · Smogový varovný a regulační systém (SVRS) checked 2026-10-27
- Státní zdravotní ústav (SZÚ) · Smogová situace – co můžeme udělat? checked 2026-10-27
- Atmospheric Composition Analysis Group (ACAG), Washington University in St. Louis · Surface PM2.5, V6.GL.02.04 (annual mean 2021-2023) checked 2026-10-27
- Copernicus Atmosphere Monitoring Service (CAMS) · CAMS global reanalysis (EAC4) checked 2026-10-27
- World Health Organization (WHO) · WHO global air quality guidelines (2021) checked 2026-10-27