Air quality this winter: how to read the AQI

Knowing how to read the Air Quality Index (AQI) helps you decide when to limit time outdoors, in winter or any season.

How the AQI works. The Central Pollution Control Board's National Air Quality Index turns measurements of up to eight pollutants, including PM2.5 and PM10, into a single number and colour. The pollutant with the worst sub-index sets the overall AQI.

The six categories (CPCB). Good (0–50): minimal impact. Satisfactory (51–100): minor breathing discomfort for sensitive people. Moderate (101–200): breathing discomfort for people with lung disease such as asthma, and discomfort for people with heart disease, children and older adults. Poor (201–300): breathing discomfort for most people on prolonged exposure. Very Poor (301–400): respiratory illness on prolonged exposure. Severe (401–500): affects healthy people and seriously affects people with lung or heart disease.

What to do (NCDC). The National Centre for Disease Control's air-pollution health advisory says vulnerable people should cut down on prolonged or strenuous outdoor exertion from Satisfactory or Moderate levels, everyone should avoid outdoor exertion at Poor, and at Very Poor or Severe vulnerable people should remain indoors and keep activity low.

Who is most at risk. Older people, children under five, pregnant women, and people with asthma or other lung or heart disease.

Check daily on the CPCB AQI website or SAFAR.

Join the El Niño help room on soshyal.com to ask questions and share what you see in your area.