Delhi pollution: CPCB says extreme PM 2.5 readings not part of AQI methodology amid Diwali data gaps

The Central Pollution Control Board on Tuesday clarified that its air quality monitoring system does not include particulate matter concentrations above 1,000 micrograms per cubic metre in hourly air quality calculations. The monitoring equipment was originally calibrated to measure concentrations only up to that level, the pollution regulator said.

The statement came amid reports that more than 20 of Delhi’s 59 air quality monitoring stations had not reported readings on Diwali night.

Air quality deteriorates sharply in the winter months in Delhi, which is often ranked the world’s most polluted capital. Peak air pollution levels are historically observed during and immediately after Diwali.

This year, the festival was celebrated on Sunday, amid worsening air quality in the capital over the past week.

CPCB Comments on reporting of National Air Quality Index (NAQI) during the post-Diwali period.@byadavbjp @KVSinghMPGonda @moefcc @PIB_India @mygovindia pic.twitter.com/5PvGg9jeIM— Central Pollution Control Board (@CPCB_OFFICIAL) November 10, 2026

The Centre for Research on Energy and Clean Air analysed the pollution control board data on Sunday night which showed that the number of stations not reporting readings rose between midnight and 2 am, when pollution levels typically peak.

At 7 pm on Sunday, only one station was not reporting data. The number rose to seven by 10 pm and 23 by 11 pm. By midnight, 29 stations had stopped reporting...

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