Very Unhealthy Air Quality (AQI 201–300)
Health alert — everyone may experience more serious health effects.
0–50
51–100
101–150
151–200
201–300
301–500
What Does This Mean?
PM2.5 is typically 150.5–250.4 µg/m³ — 10–17× the WHO guideline. This is a severe pollution event. Visibility is markedly reduced. Common during extreme inversions (Delhi winter), large-scale crop burning (Southeast Asia burning season), or major wildfires.
Who Is Affected?
- Everyone is at risk of respiratory symptoms and reduced lung function
- Sensitive groups face serious risk — emergency hospital visits increase measurably at this level
- Children should avoid all outdoor exertion
What Should You Do?
- Everyone: avoid prolonged outdoor exertion
- Sensitive groups: remain indoors with air purification
- Wear N95 masks for any outdoor time — standard surgical masks are inadequate
- Seal gaps around windows and doors
- Run multiple HEPA purifiers if available
- Schools should cancel outdoor activities
- Consider medical check-up if experiencing persistent symptoms (chest pain, severe coughing, difficulty breathing)
Key Pollutants at This Level
PM2.5 dominates. At these levels, PM10 is also typically elevated. NO₂ and SO₂ may contribute in industrial zones.