Private monitors put Chennai’s air above 1,200 on the AQI scale on Deepavali night

Firecracker smoke pushed Chennai’s air quality to extreme levels on Deepavali night, 8 November, with a private monitoring platform recording an air quality index (AQI) above 1,200, The Hindu reported.

The reading came from AQI India, a platform based in Delhi. The Central Pollution Control Board’s national index, which the government uses, runs only from 0 to 500, so the two sets of numbers cannot be compared directly. Officials said the gap comes from the different ways of working out the index.

What the readings showed

K. Srikanth, a weather blogger who runs the Chennai Rains page, said the sensor outside his home showed an AQI of about 1,000 for nearly four hours, from 6 p.m. to 10 p.m. He said bursting crackers in a short window, partly because of the rules and partly between spells of rain, made it worse. By 7 a.m. on 9 November, the reading had dropped to about 200.

He said pollution may stay high for a few days while winds blow from the north. Winds from the east, off the Bay of Bengal, should help clear the air.

A warning on the numbers

Dharmesh Shah, an environmental policy researcher, said home monitors and private platforms give a useful idea of pollution but are not fully accurate. He called for a wider network of low-cost monitors across Chennai. “Everything now is focussed on Delhi, but air pollution is a serious concern here too,” he said.

Under Indian standards, a yearly average of fine dust, or PM2.5, above 40 micrograms per cubic metre is harmful. The World Health Organization’s guideline is 5.

What to do

People with asthma or heart or lung disease, older people and young children should avoid outdoor exercise while the air is smoky, and see a doctor if they have trouble breathing.