What Is a Good AQI Level? Air Quality Index Ranges Explained

The Air Quality Index compresses several pollutants — PM2.5, PM10, ozone, nitrogen dioxide, sulphur dioxide and carbon monoxide — into a single 0-500 number. The reported AQI is always the worst single pollutant, not an average.

The six bands 0-50 Good — no precautions needed. 51-100 Moderate — unusually sensitive people may notice irritation on long outdoor efforts. 101-150 Unhealthy for sensitive groups — asthma, heart conditions, children and over-65s should shorten outdoor exercise. 151-200 Unhealthy — everyone can feel effects; move workouts indoors. 201-300 Very unhealthy — stay in, run a HEPA filter, keep windows shut. 301+ Hazardous — treat it as an emergency advisory.

Practical rules Under 50 you can do anything. Between 50 and 100, hard cardio is fine for most adults but skip it if you have asthma. Above 100, halve your outdoor session or move it to the morning, when PM2.5 is usually lowest in cities. Above 150, don't exercise outdoors at all — during exertion you inhale roughly ten times more air per minute, so the dose scales with effort.

Why your app and your neighbour's app disagree The US EPA scale and the European CAQI scale use different breakpoints, so the same air can read 78 on one and 41 on the other. Compare the raw PM2.5 figure in µg/m³ instead: the WHO 24-hour guideline is 15 µg/m³.