Why was AQI data missing on Diwali night? CPCB clarifies
What's the story
The Central Pollution Control Board (CPCB) has responded to allegations of under-reporting air pollution data during and after Diwali. The board clarified that the discrepancies between its official figures and private air quality apps are due to scientific methodology and hardware limitations. On Diwali, while the CPCB's Sameer app showed AQI numbers around 400 in the 'severe' category, private platforms showed AQI even above 1000, making netizens question the government numbers.
Data
227 missing hourly observations
An analysis by the Centre for Research on Energy and Clean Air (CREA) also found that the number of stations not reporting readings climbed from seven at 10:00pm on November 8 to 23 at 11:00pm, 29 at midnight and 36 at 1:00am. Between midnight and 5:00am, CREA discovered 227 missing hourly observations at 59 stations.
Instrument limitations
Why were there data gaps?
The CPCB explained that the data gaps observed during Diwali were due to older particulate matter analyzers, which were calibrated for a measurement range of 0-1,000 micrograms per cubic meter.
These instruments treat readings above this range as errors, leading to exclusion from the final computation.
"During extreme episodes....like Diwali firecracker bursting, this may appear as data gap at the particular station concerned, and those hours do not contribute to the 24-hour average of relevant pollutant for the concerned station."
Twitter Post
Read their post here
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
AQI comparison
Why do private apps show higher AQI?
The CPCB also addressed why private apps often show higher AQI numbers than its platform.
It said private apps react to hourly spikes, while the CPCB's National Air Quality Index (NAQI) reflects exposure over the preceding 24 hours.
"It is generally perceived that private apps show higher AQI. This may hold during short peaks, when hourly values rise sharply. However, when concentrations fall, such apps show lower AQI than the NAQI...since NAQI continues to reflect the exposure of...preceding 24 hours."
Network upgrade
CPCB is upgrading its monitoring network
To reduce missing AQI data in the future, the CPCB is continuously upgrading its monitoring network, it said.
The board said older instruments are being replaced and the network expanded to avoid data dropouts during extreme pollution events.
"CPCB remains committed to transparent, scientific and reliable reporting of air quality and to continuous improvement of the monitoring network," it said.