Amid concerns over data gaps, higher AQI on private platforms, CPCB clarifies

The Central Pollution Control Board (CPCB) addressed concerns over data gaps and higher Air Quality Index (AQI) on private platforms following criticism of pollution monitoring gaps, especially during Diwali night. The CPCB clarified that its monitors, calibrated between 0–1,000 micrograms per cubic metre (μg/m³), treat hourly readings beyond this range as "outside range."

On Sunday, Delhi experienced its worst Diwali-day air quality since 2021, with multiple stations recording values as high as 5,000 µg/m³ during the same period, as reported by the Indian Express. The CPCB stated that during extreme episodes like Diwali firecracker bursts, data gaps may appear at particular stations, and those hours do not contribute to the 24-hour average of relevant pollutants.

The authority also defended its National Air Quality Index (NAQI) against criticisms that it caps the upper limit at 500, similar to the methodologies used by the United States Environmental Protection Agency and China. The CPCB explained that AQI is calculated based on a running 24-hour average or eight hours for ozone and carbon monoxide, with the highest sub-index reflecting the index.

Private apps may show higher AQI due to data from different sources and potentially different breakpoints, but when concentrations fall, these apps show a lower AQI than the national index, as it reflects exposure over the preceding 24 hours.