Pollution board explains why Diwali air monitors left blanks

The Central Pollution Control Board stated on Tuesday that its air monitors could not capture peak pollution levels on Diwali night because their analysers only measure up to 1,000 micrograms per cubic metre. Readings going past this limit are marked as outside range. Delhi saw its worst Diwali air quality since 2021 on Sunday. The watchdog gave this explanation after 45 of the 59 monitoring stations missed hourly readings for at least one pollutant. The Indian Express reported on Monday that portal stations recorded blank hourly spaces because fine particle loads from burning went past 1,000 micrograms per cubic metre. Delhi Pollution Control Committee data showed some stations crossed 5,000 micrograms per cubic metre during that time. The pollution watchdog operates under the Union Environment Ministry. It said that during extreme events like firecrackers, this shows up as a data gap, and those hours are left out of the 24-hour average.

CPCB Defense

The board noted that internal talks on handling data beyond system limits are underway, hinting at a system review. It defended capping the Air Quality Index at 500 by saying countries like the United States and China use similar rules. The board developed the National Air Quality Index in 2015 to show air status simply. The index uses eight pollutants including PM 2.5 and lead. A station needs 16 hours of data out of 24 to make a sub-index.

Private Apps

Addressing higher readings on private platforms, the board said those apps use data from sources not cleared under national standards, including low-cost sensors. These apps use instantaneous readings while the national index uses 24-hour or 8-hour averages. The board added that private apps show higher numbers during peaks, but show lower numbers than the national index when pollution falls.

Context

Air quality monitoring systems use fixed calibration limits to ensure data accuracy over long periods. When pollution spikes dramatically beyond normal design bounds during heavy firecracker use, standard equipment reaches its technical limit. Understanding these technical gaps helps scientists improve future monitoring equipment.