On the morning after Deepavali, Delhi woke to air that was hard to breathe and harder to measure. The city's average air quality index stood at 370, a level India's Central Pollution Control Board calls very poor, and many neighbourhoods recorded readings above 400, which the board calls severe. The numbers spread quickly online, and so did figures far above the official ones. This article sorts the verified facts from the noise, explains what the index actually measures, and sets out what the emergency rules now in force mean for people living through it.

The story matters beyond Delhi. Lahore, across the border in Pakistan, topped a live global ranking of polluted cities on the same morning, and the same winter pattern, cold and still air trapping smoke and dust close to the ground, returns to northern South Asia every year. Understanding one city's bad-air week is therefore useful across the region.

What happened in Delhi after Deepavali

Deepavali fell on the night of 8 November 2026. India's Supreme Court had said earlier in the month that only certified low-polluting firecrackers could be used, and only during limited hours over the festival weekend. Reuters reported that revellers in Delhi and Mumbai set off firecrackers until late into the night, and the city's air, already poor for more than a week, deteriorated further. By 9am on Monday 9 November, the Central Pollution Control Board's average reading for Delhi was 370. The board counts anything up to 50 as good. Many parts of the city were above 400, in the severe band.

The festival was not the only cause, and it is important not to blame it for everything. Reuters reported that northern India faces this problem every year from the onset of winter, when cold, heavy air traps vehicle emissions, construction dust and smoke from crop-waste burning close to the ground. In big cities, vehicles and construction make it worse. Fireworks added a sharp spike on top of a problem that was already there, so the air was bad before the festival too.

Delhi AQI: how to read the number

The air quality index, or AQI, turns several pollutants into a single number so that anyone can read it at a glance. In India the Central Pollution Control Board groups the number into six bands: 0 to 50 is good, 51 to 100 is satisfactory, 101 to 200 is moderate, 201 to 300 is poor, 301 to 400 is very poor, and 401 to 500 is severe. A reading of 370 therefore sits near the top of the very poor band, and a reading above 400 is severe. The band matters more than the exact number.

The pollutant that drives most bad-air days in Delhi is PM2.5, fine particles 2.5 micrometres across or smaller. They are small enough to pass deep into the lungs and into the bloodstream, which is why they dominate health advice. PM10, particles up to 10 micrometres across, is also measured. The World Health Organization's guideline for PM2.5 is an annual average of 5 micrograms per cubic metre, and a 24-hour average of 15. Delhi's readings on a very poor day are many times those levels, so people with asthma, heart disease or other long-term conditions should limit time outdoors when the index is high.

Why the readings do not all agree

If you looked at several sources on Monday morning, you may have seen different numbers for Delhi, and the disagreement itself became part of the story. The Hindu reported that PM2.5 readings were unavailable at 25 of Delhi's 39 monitoring stations on Deepavali night, a gap flagged by Congress leader Ajay Maken. The Aam Aadmi Party alleged that the data had been manipulated by shutting stations down. The Bharatiya Janata Party's Kapil Mishra denied that and alleged a conspiracy, pointing to stubble burning in Punjab. These are political claims, and none of them has been proved by an official inquiry. What is established is that the network had gaps on the night people most wanted readings.

There are also honest reasons why readings differ. A city average is not the same as a reading at one station, an hourly figure is not the same as a 24-hour average, and a private platform may use a different scale from the official one. That is why this article uses the board's city average of 370 for Monday morning, as reported by Reuters, and treats figures far above the official readings as unverified. When sources disagree, the careful course is to use the lower, official figure.

What GRAP Stage III changes on the ground

On Friday 7 November, the Commission for Air Quality Management invoked Stage III of the Graded Response Action Plan, the emergency system for Delhi and the National Capital Region, after the city's average AQI reached 382, up from 369 the day before. The plan has four stages: Stage I applies when the air is poor, from 201 to 300; Stage II when it is very poor, from 301 to 400; Stage III when it is severe, from 401 to 450; and Stage IV when it is severe plus, above 450. Stage III was called on the forecast that the air would reach the severe band. You can check the current position on our GRAP stage today page.

Stage III brings a ban on non-essential construction and demolition work, restrictions on BS-III petrol and BS-IV diesel vehicles, and rules for hybrid vehicle classes up to Class 5. It also closes polluting industries that use fuels not approved under the plan, shuts stone crushers and suspends mining. Schools in Delhi moved to online classes, as Reuters reported. They do not clear the air overnight, and they are lifted only when the index improves.

What the air does to health, and what helps

Very poor air irritates the eyes, nose and throat, and it makes breathing harder for people with asthma or chronic lung disease. It can also strain the heart. The standard advice is to stay indoors as much as possible on severe days, keep windows shut, and avoid outdoor exercise, especially in the morning when the air is often at its worst. A well-fitted mask can help outdoors, but a loose cloth mask does little against fine particles. People who feel chest pain, severe breathlessness or worsening asthma should seek medical help rather than waiting for the air to clear. Our smog-season guide explains the morning pattern and the steps that actually help.

Lahore, and the wider picture

Delhi was not alone. Reuters reported that Lahore topped IQAir's live ranking of the world's most polluted cities on Monday morning, with an AQI of 563, which the ranking describes as hazardous. The same winter weather that traps pollution over Delhi does the same over Lahore, and the two cities often share bad-air days. Anyone in Lahore can check the current picture on our smog in Lahore page, and readers elsewhere can compare with the US air quality page and the UK air quality page.

What our records show, and what they miss

Our records track official warnings and verified incidents, and they show the pattern behind this week: a forecast that pointed to severe air, an emergency plan invoked before the festival, and a city average that stayed in the very poor band. What they do not show is the air on any single street, because stations are spread thinly and some reported no data on Deepavali night. They also do not show how many people fell ill, because hospitals do not report that in real time. A single AQI number is a useful warning, not a full picture, and it should be read alongside the official forecast and the local rules in force. See today's incidents for the latest verified warnings.

The short version

  • Delhi's average AQI was 370 on the morning of 9 November, very poor, with many areas above 400.
  • GRAP Stage III is in force across Delhi-NCR, with construction and vehicle restrictions and schools online.
  • Readings differed because 25 of 39 stations reported no PM2.5 data on Deepavali night; unverified social-media figures should be ignored.
  • PM2.5 is the main danger; stay indoors on severe days and seek help for severe breathlessness or chest pain.
  • Lahore was ranked the world's most polluted city the same morning, at 563 on IQAir's live ranking.