What should you do during an air pollution episode?

Short answer. During an air pollution episode, follow your local alert: reduce intense physical activity, especially if you are vulnerable, and avoid busy roads at rush hour ²³. Do not add pollution: no open fires or old wood stoves, fewer solo car trips ³. Triggers differ by country: France starts its alert procedure at a daily mean of 80 µg/m³ of PM10 ³, Poland at 150 µg/m³ ⁵.

What is an air pollution episode?

An episode is a period when pollution is above, or forecast to rise above, an official threshold over a wide area. In France it is defined as a measured, modelled or forecast exceedance of a regulatory threshold that covers at least 25 km² of a département (100 km² of a region) or at least 10% of its population (50,000 residents in smaller départements) ³. Outdoor air harms health even outside episodes: the WHO estimates it caused 4.2 million premature deaths worldwide in 2019, and 99% of the world's population lived in places that did not meet its guideline levels ¹.

There are two main types:

• Winter particle smog. Weather that keeps pollutants from dispersing combines with extra smoke from home heating. Polish alerts name the cause directly: weather conditions that block the dispersion of pollutants while emissions from household heating rise ⁵. A December 2024 alert in Lower Silesia recorded a daily PM10 mean of 195 µg/m³ in the town of Nowa Ruda ⁵.
• Summer ozone episodes. Ozone forms in strong sunlight from nitrogen oxides and volatile organic compounds ⁴, so these episodes come with hot, sunny weather. Ozone is often highest in the middle or late afternoon, while particles are often highest in the early morning and the evening ².

For wildfire smoke, see wildfire smoke.

How do authorities announce an episode?

Each country uses its own scale and triggers. To read the scales themselves, see the air quality index guide.

France. At the information level, the prefect issues health and behaviour advice; when an episode persists, the procedure moves to alert, which brings compulsory measures ³. These can include speed limits lowered by 20 km/h (130 → 110 km/h on motorways) and the suspension of exemptions for burning garden waste in the open ³. If the alert is severe or lasts, the prefect can order circulation différenciée: only vehicles with a Crit'Air sticker allowed under the order may drive. In the Loiret model order, Crit'Air 4, 5 and unclassified vehicles are banned, while cars carrying at least 3 people are exempt ³. Breaking the order brings a fine and possible impoundment ³.

India. When the Delhi AQI reached 354 on 16 January 2026, the Commission for Air Quality Management invoked Stage III as a precaution, on top of Stages I and II already in force ⁸. It restricted dusty construction across the NCR, and BS-III petrol and BS-IV diesel cars in Delhi and four nearby districts ⁸.

What should you do at home?

• Ventilation. France's health ministry says not to change your usual airing habits, because an episode does not justify staying shut in, and to air your home during the least polluted hours ². Poland's warnings say the opposite: "do not air rooms" and "limit airing" ⁵. See the comparison below.
• Heating with wood. France asks people to stop using inefficient wood-burning appliances, in particular open fireplaces and old stoves used for comfort rather than as the main heat source ³. Poland says not to light the fireplace ⁵; Delhi asks citizens not to use coal or wood for heating ⁸.
• Other indoor sources. Avoid adding irritants: tobacco smoke, solvents used indoors, wood heating ³. Postpone garden work with petrol tools ³.
• A clean room. If someone at home is very sensitive, see how to set up a clean-air room.

What should you do outside?

• Sport. The general population needs no change at the information level, but should reduce high-intensity activity at the alert level ². Vulnerable and sensitive people should limit intense activity at the information level and avoid it at the alert level ². France says moderate activity stays acceptable for everyone, and that the health benefits of cycling and running outweigh the risks ².
• Timing and place. Exercise away from major roads and during the least polluted hours ². On ozone days, Germany advises sensitive people such as asthmatics to avoid physical effort outdoors in the afternoon ⁴.
• The car. Avoid driving alone; use public transport or carpooling; drive smoothly at lower speed ³. Delhi adds working from home where possible and combining errands ⁸.
• Masks. Poland advises using anti-smog masks only after consulting a doctor ⁵.

Who needs extra care?

France lists pregnant women, infants and young children, people over 65, and people with heart disease, heart or respiratory failure or asthma as vulnerable ². Poland adds people with cancer ⁵. The UK advises at-risk people to follow their agreed management plan, such as an asthma action plan, and to see a doctor or nurse if symptoms are new, get worse or do not improve after a week ⁶. Poland notes that people with asthma may need their medicines more often than usual ⁵; any change to a treatment should be decided with a doctor ². For the full checklist, see sensitive people and polluted air.

What about children at school?

Infants can still go out, but outings should be shorter near major roads and at the most polluted hours ². Older children should limit high-intensity activity; light to moderate activity can continue indoors and outdoors ². Rules for schools can be stricter: one Polish regional short-term plan bans outdoor activity for pupils during an alarm ⁵, and Delhi's Stage III moved classes up to class V to hybrid mode, with the online option left to students and their guardians ⁸. Check your school's or district's own rules.

What official agencies recommend

• France. Keep usual ventilation, limit intense exercise if vulnerable, avoid wood heating and solo car trips ²³.
• Germany (Umweltbundesamt). Behaviour advice from 180 µg/m³ of ozone; sensitive people avoid afternoon effort outdoors ⁴.
• Poland (GIOŚ). Avoid intense outdoor effort, do not air rooms; vulnerable people should stay indoors if they can ⁵.
• United Kingdom (Defra). From the high band, everyone should try to reduce exposure, and at-risk people should adapt demanding outdoor activity ⁶.
• United States (AirNow). Watch for Action Days declared by local agencies ⁷.
• India (CAQM). Follow the GRAP citizen charter: walk or cycle, share rides, no coal or wood heating ⁸.

Where they differ:

• Windows. France keeps normal airing and warns against shutting yourself in ²³; Poland says not to air rooms ⁵. Follow your local alert's wording.
• Thresholds. France's PM10 alert level (80 µg/m³) is close to half of Poland's alarm level (150 µg/m³) ³⁵, so an alert does not mean the same air in both countries.
• Who acts. France and India can impose compulsory traffic measures ³⁸; the UK DAQI is a scale of health advice for each band ⁶.

Frequently asked questions

Should I close the windows during a pollution episode?

It depends on the country. France says to keep your usual airing habits and choose the least polluted hours ². Poland's warnings say not to air rooms ⁵. If in doubt, follow the wording of your local alert.

Can I still go running?

Yes, at a lower intensity for most people. France says the benefits of running and cycling outweigh the risks, and that the general population only needs to cut high-intensity effort at the alert level ². Run away from main roads, and in the morning on ozone days ²⁴.

Is my car allowed during an episode in France?

Yes, unless the prefect has ordered circulation différenciée and your Crit'Air class is excluded. In the Loiret model order, Crit'Air 4, 5 and unclassified vehicles are banned, and cars carrying 3 or more people are exempt ³.

Before the next episode

For air and water risks country by country, see /air.

The Phaenyx plan's "Water and air" section lists the water and air risks for your postcode. The Phaenyx Safe app keeps the reflex sheets available offline. See the Phaenyx plan.

Sources

1. World Health Organization (WHO) — Ambient (outdoor) air pollution — https://www.who.int/news-room/fact-sheets/detail/ambient-(outdoor)-air-quality-and-health (accessed 2026-10-27)
2. Santé.fr (French Ministry of Health) — Recommandations en cas d'épisode de pollution — https://www.sante.fr/node/2637849 (accessed 2026-10-27)
3. Préfecture du Loiret / DREAL Centre-Val de Loire — Arrêté préfectoral du 16 novembre 2017 relatif aux épisodes de pollution de l'air ambiant (Loiret) – Annexes — https://www.centre-val-de-loire.developpement-durable.gouv.fr/IMG/pdf/45_-_2017_11_16_ap_pollution_atmo_annexes.pdf (accessed 2026-10-27)
4. Umweltbundesamt (German Environment Agency) — Ozon — https://www.umweltbundesamt.de/themen/luft/luftschadstoffe-im-ueberblick/ozon (accessed 2026-10-27)
5. Główny Inspektorat Ochrony Środowiska (GIOŚ, Poland) — Powiadomienie o przekroczeniu poziomu alarmowego i o ryzyku wystąpienia przekroczenia poziomu alarmowego dla pyłu zawieszonego PM10 w powietrzu (województwo dolnośląskie, 30.12.2024) — https://powietrze.gios.gov.pl/pjp/documents/download/115747 (accessed 2026-10-27)
6. Department for Environment, Food & Rural Affairs (Defra), GOV.UK — Health advice for the Daily Air Quality Index (DAQI) — https://www.gov.uk/government/publications/health-effects-of-air-pollution/health-advice-for-the-daily-air-quality-index-daqi (accessed 2026-10-27)
7. AirNow (U.S. EPA and partner agencies) — Action Days — https://www.airnow.gov/aqi/action-days/ (accessed 2026-10-27)
8. Press Information Bureau, Government of India (Commission for Air Quality Management) — CAQM invokes GRAP Stage-III in Delhi-NCR with immediate effect — https://www.pib.gov.in/PressReleasePage.aspx?PRID=2215456 (accessed 2026-10-27)