Several Delhi air-quality monitoring stations, including those in RK Puram, Nehru Nagar, Mundka, Sonia Vihar and Dwarka, stopped displaying readings after 9 pm on Diwali night.
Before its data disappeared, RK Puram recorded PM2.5 levels of 924 micrograms per cubic metre, while the JNU station reported 786 micrograms per cubic metre by 11 pm.
The outages raised questions about monitoring reliability, particularly as earlier reports had also identified missing data across Delhi's pollution-monitoring network.
Several key air-quality monitoring stations in Delhi stopped displaying real-time pollution data on Diwali evening, just as particulate matter concentrations were rising sharply across the national capital, raising questions about the reliability and transparency of the city's pollution-monitoring network. Stations in areas including RK Puram, Nehru Nagar, Mundka, Sonia Vihar and Dwarka stopped providing readings for several hours after 9 pm.
The interruptions came as Delhi residents burst firecrackers despite restrictions, with available readings indicating a sharp deterioration in air quality.
Monitoring Stations Go Blank As PM2.5 Levels Rise
Before its data stopped appearing, the RK Puram monitoring station recorded a PM2.5 concentration of 504 micrograms per cubic metre at around 8 pm. The reading reportedly climbed to 924 micrograms per cubic metre by 9 pm, after which the station stopped displaying data. PM2.5 refers to fine particulate matter that can penetrate deep into the lungs and enter the bloodstream.
The Jawaharlal Nehru University (JNU) monitoring station, located in a comparatively less populated part of South Delhi, continued reporting readings during the same period. Its PM2.5 concentration rose from 161 micrograms per cubic metre at 8 pm to 786 micrograms per cubic metre by 11 pm, indicating a substantial increase in pollution levels even in areas where readings remained available. The contrast between the stations highlighted the difficulty of assessing the full extent of pollution when monitoring points stop transmitting data during peak hours.
The interruptions were not limited to this year's celebrations. NDTV reported that similar gaps in online pollution data had been observed on previous Diwali evenings. Such outages have often been attributed to technical glitches, although the report did not establish a definitive cause for the latest interruptions.
Technical Glitches And Gaps In Pollution Monitoring
Missing readings can occur because of problems with monitoring equipment, power supply, calibration or the transmission of data to central servers. The Delhi Pollution Control Committee (DPCC) and the Central Pollution Control Board (CPCB) operate or oversee monitoring stations that feed pollution readings to public dashboards. However, without a station-specific explanation, it cannot be established whether the Diwali outages resulted from equipment failures, communication disruptions or another technical problem.
A report by The Indian Express published on November 7 had already flagged data gaps across Delhi's monitoring network in the days before Diwali. It found that 11 stations were affected by missing readings on November 6, including gaps in PM2.5 and PM10 measurements. The report also cited DPCC's monitoring protocol, under which operational alerts are triggered when a station fails to transmit data for three consecutive hours.
Delhi's official air-quality portal states that the city's hourly AQI is calculated using readings from stations reporting during that hour. Stations without recent readings are excluded from the average and marked as not reporting. This means missing data can leave localised pollution levels out of the city's overall assessment, making reliable monitoring particularly important during periods of severe pollution.
