India’s AQI tracks 8 pollutants: PM2.5, PM10, Nitrogen Dioxide, Sulphur Dioxide, Carbon Monoxide, Ozone, Ammonia, and Lead. PM2.5 is the most harmful, 30 times thinner than human hair and able to enter the lungs and bloodstream.
India uses NAQI — the National Air Quality Index — monitored by the Central Pollution Control Board (CPCB). The scale ranges from 0 to 500.
0–50 Good: Minimal impact; 51–100 Satisfactory: Mild discomfort; 101–200 Moderate: Discomfort for lung-sensitive groups; 201–300 Poor: Breathing trouble for many; 301–400 Very Poor: Health effects; 401–500 Severe: Serious risk, stay indoors.
India monitors air quality through four systems.
The Continuous Ambient Air Quality Monitoring Stations (CAAQMS) detect pollutants continuously and give hourly updates.
Air samples are collected on filters and analysed in labs. Provides daily or periodic updates.
Satellites track particulate matter and aerosols in the atmosphere and give periodic readings.
Mobile devices are used in areas lacking permanent stations. These offer real-time local readings.
Winter, traffic and dust push Delhi’s AQI into ‘poor’ and ‘severe’ ranges. Knowing AQI helps you understand how the air affects your health — and what precautions to take.
Sometimes, AQI can differ at the same spot. This is because of different data sources, AQI scales, depending on whether the area is a residential or commercial area with traffic and time of day (higher early morning/night)
Different formulas create different AQI values. India caps at 500, while IQAir may show up to 1500. The US PM2.5 limit is 15 micrograms per cubic metre and India allows 60; the US PM10 limit is 45 and India allows 100.