Delhi’s air: monitoring stations went silent at the worst of Deepavali night

Several of the Delhi government’s air monitoring stations stopped reporting data during the night of 8–9 November, just as pollution from Deepavali fireworks peaked, The Hindu reported on 9 November.

In parts of the city, levels of fine particles rose to more than 66 times the World Health Organization’s limit, the paper reported, as people burst crackers in spite of the ban on them.

The gaps matter because the official air quality index (AQI) is worked out from the readings that come in. PM2.5 are the finest and most harmful particles. When their hourly readings are missing, the index comes out lower than it should, said Manoj Kumar, an analyst at the research group CREA. That makes the air look cleaner than it was.

The story so far

Delhi’s air stayed close to “severe” on the morning after Deepavali, with a city average AQI of 370. Stage III of the Graded Response Action Plan, which stops most building work and some vehicles, has been in force across Delhi-NCR since 6 November. The Supreme Court is due to hear the case on vehicle pollution in Delhi and its neighbouring States on 23 November.