Delhi AQI Data Under Scrutiny: 36 of 59 Monitoring Stations Went Offline on the Most Polluted Diwali in Five Years

Delhi recorded its most polluted Diwali in five years on Sunday, 8 November 2026. But the numbers behind that headline are now under serious question — because just as the city’s air turned at its worst, most of its pollution monitors stopped reporting.

According to an analysis by the Centre for Research on Energy and Clean Air (CREA), 36 of Delhi’s 59 air quality monitoring stations had stopped sending data by 1am on Monday, 9 November. That left only 23 stations reporting at the very moment pollution levels were surging. Private monitoring platforms, meanwhile, painted a far worse picture than the official figures — one recorded an air quality reading of 637 in Delhi on Monday morning, a level classified as hazardous.

The gap between the official record and what people actually breathed has raised a simple, uncomfortable question: how bad was Delhi’s air on Diwali night, really? And can the city trust the numbers it is given?

What happened on Diwali night

Diwali fell on Sunday, 8 November 2026. Delhi’s average air quality index (AQI) for the day stood at 376, according to official data — the highest recorded on Diwali since 2021, and the worst in five years. On India’s official scale, a reading between 301 and 400 counts as “very poor”. Delhi was at the top end of that band for much of the day.

The Supreme Court had allowed only certified green firecrackers on 7 and 8 November, with bursting restricted to two windows: 6am to 7am and 8pm to 10pm. But the restrictions were widely ignored. Firecrackers went off through the night, and pollution levels climbed sharply as the evening wore on.

By 10pm on Sunday, the permitted bursting window had ended, but firecrackers kept going off through the night. A thick blanket of smog settled over the capital. By Monday morning, visibility was poor and the air was heavy. Official data put Delhi’s AQI at 370 at 8am on Monday and 371 at 10am. By 4pm on Monday, the average had eased to 344 — still “very poor”.

Those are the official numbers. The problem is what happened to the machines that produce them.

The monitors that went dark

Delhi has 59 air quality monitoring stations, run by the Central Pollution Control Board (CPCB), the Delhi Pollution Control Committee (DPCC), the India Meteorological Department and the Indian Institute of Tropical Meteorology. On Diwali night, they started dropping off the network one by one.

CREA’s analysis of the hourly data tells the story in numbers:

• At 7pm on Sunday, only one of the 59 stations was not reporting data.
• By 10pm, seven stations had stopped reporting.
• By 11pm, the number had risen to 23.
• By midnight, 29 stations were silent.
• By 1am on Monday, 36 stations — more than six in ten — had stopped reporting, leaving just 23 still sending readings.
• At 2am, 35 stations were still not reporting.

In other words, during the worst hours of the night, when pollution was at its peak, most of Delhi’s monitoring network was blind.

A separate analysis by the Hindustan Times found that 42 percent of the expected hourly PM2.5 readings from 39 monitoring stations were missing between 10pm and 6am on Diwali night.

It was not a single station or a single neighbourhood. According to NDTV, the DPCC’s website stopped showing real-time data from stations including R.K. Puram, Nehru Nagar, Mundka, Sonia Vihar and Dwarka. R.K. Puram had recorded fine particulate matter (PM2.5) levels of 504 micrograms per cubic metre before its data stopped appearing after 9pm. The concentration there had reportedly reached 924 micrograms per cubic metre by 10pm.

Even on Monday afternoon, the network had not fully recovered. At 4pm on Monday, only 47 of the 59 stations were recording data. Of those, 40 were in the “very poor” category and seven in the “poor” category. Bawana recorded the worst AQI at 396, followed by Burari at 393.

What the private monitors showed

While the official network was going quiet, private air quality platforms were recording far worse pollution than the government figures suggested.

AQI.in, a private monitoring platform, recorded an air quality reading of 637 for Delhi on Monday morning, classifying the air as hazardous. Swiss platform IQAir recorded an AQI of 245 on the US scale at 8.30am on Monday, in the “very unhealthy” category, with PM2.5 concentrations at 170 micrograms per cubic metre — around 34 times the World Health Organization’s annual guideline value.

The raw pollution readings from the stations that did keep working were extreme. According to The Hindu, data from the DPCC showed that Punjabi Bagh recorded a PM2.5 concentration of 993 micrograms per cubic metre at 4am on Monday — approximately 66 times the WHO’s recommended 24-hour limit of 15 micrograms per cubic metre. Vivek Vihar recorded 873 micrograms per cubic metre at 2am. R.K. Puram registered 924 at 10pm on Sunday.

Several CPCB stations recorded extremely high PM2.5 concentrations on Monday. Siri Fort logged a maximum of 1,000 micrograms per cubic metre up to noon — the highest value the CPCB’s public portal displays, because the portal does not show readings above 1,000.

Delhi’s average PM2.5 concentration on Diwali itself stood at 257 micrograms per cubic metre, according to The Tribune.

The gap between the official average and the private readings is not just a technical detail. The AQI is the number the public, the media and policymakers use to judge how dangerous the air is. If the official average is calculated from only the stations that happened to keep working — and if the stations that went dark were among the worst affected — then the published figure may understate what people actually breathed.

Why the stations stopped reporting

So far, there is no clear official explanation for why so many stations stopped reporting at the same time.

Experts who tracked the numbers in real time have criticised the failure. Anumita Roychowdhury, executive director of the Centre for Science and Environment (CSE), has been among those questioning why the monitoring network failed to provide real-time data during a public health emergency.

This is not the first time it has happened. Similar disruptions were observed on Diwali night last year as well, with technical glitches often cited as the reason. NDTV pointed out that interruptions in online pollution data were also seen last Diwali. The pattern — monitors failing on the one night of the year when pollution peaks — is now a recurring feature of Delhi’s Diwali, and experts say that is exactly why it needs a proper explanation.

Delhi cabinet minister Kapil Mishra was asked about the missing readings at a press conference. He asked reporters to share details of the monitoring stations reported to be non-functional, saying he would seek action on the matter.

The political row

The missing data quickly became a political issue. Senior Aam Aadmi Party (AAP) leader Saurabh Bharadwaj accused the Delhi government of manipulating pollution figures. The AAP alleged that dozens of monitoring stations operated by the CPCB, DPCC, IMD and IITM had gone offline as pollution levels rose on Diwali night and resumed functioning the following morning.

The party had made a similar allegation after Diwali last year, accusing the BJP-led Delhi government of deliberately switching off air quality monitoring stations to conceal the rise in pollution levels.

There is no evidence so far that the stations were switched off deliberately, and the government has not accepted the allegation. But the accusation, combined with the scale of the data gap, has put the monitoring system itself at the centre of the debate — rather than just the pollution.

Why this matters

Delhi’s air pollution is a public health issue, not just a weather story. PM2.5 — the tiny particles that make up the most dangerous part of smog — can get deep into the lungs and into the bloodstream. The WHO’s recommended 24-hour limit is 15 micrograms per cubic metre. On Diwali night, Delhi recorded levels more than 60 times that limit in some areas.

When the official numbers understate the problem, several things go wrong at once. People make decisions about whether to go outside, whether to send children to school, and whether to wear a mask based on the published AQI. If that number is built on incomplete data, those decisions are based on a false picture. Emergency measures, such as restrictions on vehicles or construction, are also triggered by AQI thresholds — so missing data can delay the response.

There is also a longer-term cost. Delhi’s air quality record is used to track whether policies are working, year after year. If the worst nights keep disappearing from the record because the monitors go dark, the trend looks better than it really is.

What happens next

The immediate question is whether the monitoring network will be fixed and independently checked before the next pollution peak. Delhi’s air usually gets worse through November and December, as cold air traps pollution close to the ground and stubble burning in neighbouring states adds to the load. The city has not yet seen its worst air of the season.

The missing readings from Diwali night are also likely to feature in the ongoing legal and political scrutiny of Delhi’s air quality. The Supreme Court has been closely involved in the issue, including the rules on firecrackers for this year’s Diwali. The gap in the data is now part of that record.

For now, the official verdict stands: Delhi’s most polluted Diwali in five years, with an average AQI of 376. But the evidence suggests the real figure was higher — and nobody can say by how much, because the machines that were supposed to measure it had stopped working.

Frequently asked questions

What was Delhi’s AQI on Diwali 2026?

Delhi’s average AQI on Diwali day, Sunday 8 November 2026, was 376 according to official data — the highest on Diwali since 2021 and the most polluted Diwali in five years. The reading falls in the “very poor” category.

How many air quality monitoring stations went offline in Delhi on Diwali night?

Of Delhi’s 59 monitoring stations, 36 had stopped reporting data by 1am on Monday, 9 November, leaving only 23 stations still sending readings. More than 20 stations were without data between midnight and 2am, during the peak smog hours.

Why did the monitoring stations stop reporting?

There is no confirmed official explanation yet. Technical glitches have been cited for similar disruptions in previous years. The AAP has alleged the stations were deliberately switched off to hide the true pollution levels, but there is no evidence so far to support that claim.

How bad was Delhi’s air according to private monitors?

Private platforms recorded much worse pollution than the official figures. AQI.in recorded a reading of 637 on Monday morning, classified as hazardous. IQAir recorded PM2.5 concentrations of 170 micrograms per cubic metre at 8.30am — around 34 times the WHO’s annual guideline value.

What is PM2.5 and why does it matter?

PM2.5 refers to fine particles in the air that are smaller than 2.5 micrometres across. They are small enough to get deep into the lungs and into the bloodstream. The WHO recommends that average exposure over 24 hours should not exceed 15 micrograms per cubic metre. Some Delhi stations recorded levels close to 1,000 micrograms per cubic metre on Diwali night.

Conclusion

Delhi’s Diwali story this year has two parts. The first is familiar: the worst Diwali air in five years, with firecrackers pushing pollution to dangerous levels despite court restrictions. The second is new, and in some ways more worrying: the system built to measure that pollution failed at the moment it was needed most.

Thirty-six of 59 monitoring stations went silent on the worst night of the year. Private monitors suggest the real pollution was far worse than the official figures show. And this has happened before — the same gaps appeared last Diwali, with no clear explanation then either.

Until Delhi can keep its monitors running on the nights when the air is at its worst, the city will not really know how bad its pollution gets. And without honest numbers, it cannot fix the problem.

Sources

• Deccan Herald: https://www.deccanherald.com/india/delhi/questions-over-delhi-aqi-data-as-several-monitoring-stations-go-offline-on-diwali-night-4212731
• The New Indian Express: https://www.newindianexpress.com/cities/delhi/2026/Nov/09/delhi-aqi-data-under-scrutiny-as-monitoring-stations-go-offline-amid-peak-diwali-pollution
• Rediff: https://www.rediff.com/news/report/delhi-aqi-data-questioned-as-stations-go-offline-on-diwali-night/20261109.htm
• The Times of India: https://timesofindia.indiatimes.com/city/delhi/data-eclipse-experts-flag-delhi-aqi-data-gap-on-diwali-night-after-36-of-59-pollution-monitoring-stations-go-offline/articleshow/135681086.cms
• The Tribune: https://www.tribuneindia.com/news/delhi/capital-struggles-in-toxic-air-after-diwali/
• The Wire: https://m.thewire.in/article/environment/sixty-six-times-the-who-limit-42-of-readings-missing-delhis-toxic-air-has-a-data-problem-again

This article is for general information and education only. It is not legal or financial advice.