As pollution soared, majority of Delhi's air monitors went offline

As Delhi's skyline lit up unabated on Diwali night, the levels of pollutants skyrocketed far beyond permissible limits across the city. But at the very moment when tracking dangerous pollution peaks was most critical, the majority of Delhi's 39 continuous ambient air quality monitoring stations (CAAQMS) went offline for hours, creating significant data gaps.

- Jasjeev Gandhiok

An analysis of Central Pollution Control Board (CPCB) and Delhi Pollution Control Committee (DPCC) data by HT revealed that only nine stations — barely 23% of the city's monitoring network—recorded continuous data. The remaining stations logged blackouts ranging from one to nine hours during the crucial 36-hour period between midnight on Monday and 11am Tuesday.

Dwarka Sector 8 recorded the poorest performance, with data available for only 27 of the 36 critical hours. Monitoring stations at Jawaharlal Nehru Stadium, Nehru Nagar, Patparganj, and RK Puram each lost approximately eight hours of readings.

Four other stations missed only one hour, but 10 crucial monitoring points went dark for six hours or more during the period when firecracker emissions typically peak.

Data gaps, pollution spikes

Experts stressed that the missing data is not a new phenomenon. Every year, several stations stop reporting when pollution levels spike during Diwali, suggesting the system's inability to handle pollution loads beyond a certain threshold.

"The observed pattern shows that most stations stopped providing data when they approached 1,000 µg/m³, while there were stations such as Anand Vihar, Nehru Nagar, Mundka, that recorded values above 1,000 µg/m³, indicating that the technology of monitoring isn’t an issue, at least in terms of being available. We have observed this over the past years too," said Sunil Dahiya, founder and lead analyst of think tank EnviroCatalysts.