📷 Image: Wikimedia Commons / Goutam1962
Weather
CPCB says AQI cap of 500 hid Delhi’s worst Diwali smog, explains monitor lapse
✍️ Livemint
🗓 11 Nov 2026, 10:23 AM
👁 9
The Central Pollution Control Board clarified that the official AQI ceiling of 500 prevented the recording of the city’s peak pollution levels during Diwali, citing gaps in monitoring coverage.
Delhi’s air quality deteriorated sharply during the Diwali celebrations, with satellite data and independent sensors indicating particulate matter concentrations far above the national safe limits. While the public saw AQI values pegged at the maximum of 500 on official portals, the Central Pollution Control Board (CPCB) has now explained why the reported figure did not capture the true peak of the smog.
According to the CPCB, the AQI reporting system is programmed to cap values at 500 to avoid numerical overflow in its public dashboards. When pollutant levels exceed this threshold, the system records the maximum value rather than the actual concentration. Additionally, the board noted that several of its continuous monitoring stations were either offline or operating on reduced frequency during the festival, leading to an incomplete picture of the ambient air quality.
The board emphasized that the capped figure should not be interpreted as an indication that pollution was under control. It urged citizens to rely on real‑time data from independent networks and warned that health advisories remain in force until comprehensive measurements are restored. The CPCB also announced plans to upgrade its monitoring infrastructure to ensure uninterrupted data flow during future high‑pollution events.
According to the CPCB, the AQI reporting system is programmed to cap values at 500 to avoid numerical overflow in its public dashboards. When pollutant levels exceed this threshold, the system records the maximum value rather than the actual concentration. Additionally, the board noted that several of its continuous monitoring stations were either offline or operating on reduced frequency during the festival, leading to an incomplete picture of the ambient air quality.
The board emphasized that the capped figure should not be interpreted as an indication that pollution was under control. It urged citizens to rely on real‑time data from independent networks and warned that health advisories remain in force until comprehensive measurements are restored. The CPCB also announced plans to upgrade its monitoring infrastructure to ensure uninterrupted data flow during future high‑pollution events.