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

Short answer. The Environment Agency (ARSO) posts the day's air quality warnings on one page; if nothing is posted, there is no warning that day ¹. For live levels, the European Environment Agency's index rates every station in six levels, from "good" to "extremely poor" ³. Particle pollution peaks in winter in basins such as Ljubljana, Celje and Zasavje; ozone peaks in summer, especially in Primorska ⁸.

Where can I check air quality right now?

ARSO measures sulphur dioxide, nitrogen oxides, carbon monoxide, ozone, organic compounds and PM10 and PM2.5 particles across a national network, and publishes the results ². Its warnings page carries current air warnings: "if nothing is posted, there is no warning for that day" ¹. The National Institute of Public Health (NIJZ) asks residents to follow ARSO's air quality notices and forecasts ⁴⁵.

The European Air Quality Index covers Slovenia with hourly station data, a modelled map and 48-hour forecasts, and has a mobile app ³.

What do the index levels mean?

Phaenyx found no national index scale published by ARSO. NIJZ points to the EEA's European Air Quality Index as an example of an index ⁶. The EEA index has six levels: good, fair, moderate, poor, very poor and extremely poor; for PM2.5, "good" is 0-5 µg/m³ and "poor" is 51-90 µg/m³ ³. It shows short-term (hourly) conditions, not the long-term situation ³.

NIJZ also publishes its own table of advice by 24-hour PM10 concentration ⁴. It is NIJZ's own table, separate from the EEA levels above:

*Adults with lung or heart disease, older people and children ⁴. See Air quality index explained.

How polluted is the air on average?

The population-weighted median of Slovenian cities shows about 13 µg/m³ of PM2.5 (annual mean 2021-2023) ⁹, more than twice the WHO guideline of 5 µg/m³ ¹¹. Nitrogen dioxide is about 11.2 µg/m³ ¹⁰, just above the WHO guideline of 10 µg/m³ ¹¹. That NO2 figure is a regional background over roughly 80 km: a busy street will be higher.

NIJZ says the most polluted places are basin towns in winter, when temperature inversions trap pollutants (Ljubljana, Celje, Zasavje); the main causes are traffic and household heating, as well as industry ⁸.

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

• Winter particle episodes: limit time outdoors to the cleanest part of the day, avoid busy roads, prefer a walk to strenuous exercise, air your home when pollution is lowest, use HEPA filters in ventilation systems, and do not smoke or light candles indoors. People with asthma, COPD or heart disease should keep taking their treatment and keep quick-relief medicine at hand ⁵.
• Summer ozone: concentrations are highest in Primorska, partly from ozone carried from northern Italy; at Nova Gorica and Koper they peak between 13:00 and 17:00 ⁶. On days when the information or alert threshold is exceeded at the Otlica station, avoid outdoor physical activity on the Trnovo-Banjšice plateau ⁶. See Ozone days.
• Saharan dust: it harms health in the same way as particles from traffic or heating; ARSO warns when levels are high ⁴. See Dust storms.
• Fire smoke: follow the incident commander, firefighters and civil protection, and the websites of URSZR, NIJZ and ARSO. Leave smoky areas; while there, protect your airways, for example with a well-fitting FFP mask. Indoors, close windows and doors and switch off ventilation that draws outside air; staying indoors is only a temporary solution ⁷. See Wildfire smoke, A clean-air room at home and Masks for smoke.

How official warnings reach you is on our Slovenia alerts page. A household plan can note who at home is sensitive to polluted air.

Frequently asked questions

Does Slovenia have its own air quality index?

Phaenyx found no national index scale published by ARSO. NIJZ points to the EEA index as an example and publishes its own PM10 advice table ⁴⁶.

When is air pollution worst in Slovenia?

Particles in winter in basin towns; ozone in summer, especially in Primorska ⁸.

Is staying indoors enough during fire smoke?

Only for a while: indoor levels slowly match outdoor levels even with windows closed ⁷.

Sources

1. Agencija RS za okolje (ARSO) — Zrak – opozorila — https://www.arso.gov.si/zrak/opozorila/ (accessed 2026-10-27)
2. Agencija RS za okolje (ARSO) — Kakovost zraka — https://www.arso.gov.si/zrak/kakovost%20zraka/ (accessed 2026-10-27)
3. European Environment Agency (EEA) — European Air Quality Index — https://airindex.eea.europa.eu/AQI/index.html (accessed 2026-10-27)
4. Nacionalni inštitut za javno zdravje (NIJZ) — Visoke vrednosti delcev v zunanjem zraku zaradi saharskega peska — https://nijz.si/moje-okolje/zrak/visoke-vrednosti-delcev-v-zunanjem-zraku-zaradi-saharskega-peska/ (accessed 2026-10-27)
5. Nacionalni inštitut za javno zdravje (NIJZ) — Povišane ravni delcev v zraku – priporočila za prebivalce — https://nijz.si/moje-okolje/zrak/povisane-ravni-delcev-v-zraku-priporocila-za-prebivalce/ (accessed 2026-10-27)
6. Nacionalni inštitut za javno zdravje (NIJZ) — Povišane ravni troposferskega ozona – priporočila za prebivalce — https://nijz.si/moje-okolje/zrak/troposferski-ozon-priporocila/ (accessed 2026-10-27)
7. Nacionalni inštitut za javno zdravje (NIJZ) — Napotki prebivalcem ob izpostavljenosti dimu požara — https://nijz.si/moje-okolje/zrak/napotki-prebivalcem-ob-izpostavljenosti-dimu-pozara/ (accessed 2026-10-27)
8. Nacionalni inštitut za javno zdravje (NIJZ) — Zrak — https://nijz.si/moje-okolje/zrak/ (accessed 2026-10-27)
9. 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)
10. Copernicus Atmosphere Monitoring Service (CAMS) — CAMS global reanalysis (EAC4) — https://ads.atmosphere.copernicus.eu/ (accessed 2026-10-27)
11. World Health Organization (WHO) — WHO global air quality guidelines (2021) — https://www.who.int/publications/i/item/9789240034228 (accessed 2026-10-27)