Delhi AQI crosses 400 on Diwali: Firecrackers push air quality into ‘severe’ zone as thick smog blankets city

An AQI of 406 means pollution has crossed into the CPCB's 'severe' category. This is the most polluted band on the scale and signals that air quality has deteriorated beyond the 'very poor' range. The classification helps residents and authorities understand the seriousness of pollution levels.

The CPCB classifies AQI from 0 to 50 as 'good', 51 to 100 as 'satisfactory', 101 to 200 as 'moderate', 201 to 300 as 'poor', 301 to 400 as 'very poor', and 401 to 500 as 'severe'. ITO recorded 406 at about 4:20 am on Monday. Delhi's overall AQI was 366 around 7 am, still 'very poor'.

The reading mattered because it showed pollution had moved beyond a citywide 'very poor' average in several locations. Twenty monitoring stations entered the severe category on Diwali night. The early-warning system forecast that Delhi could remain severe for several days from November 9.

Severe pollution was widespread rather than limited to one neighborhood. Of 59 stations reporting at 10 pm on Diwali, 20 recorded severe AQI, while 33 were very poor and six were poor. This shows that most reporting locations had unhealthy air, even when they had not crossed the severe threshold.

Sonia Vihar recorded the night's highest reading at 463. Jahangirpuri followed at 450. Other areas with high pollution included Burari, Alipur and Punjabi Bagh. Sonia Vihar, Jahangirpuri, Punjabi Bagh, Burari, Okhla and Rohini remained in the severe category throughout the day.

The readings continued to fluctuate at different times and stations. Rajiv Chowk recorded 381 at 1:30 am, South Extension recorded 360 at 4:00 am, and ITO reached 406 around 4:20 am. Delhi's overall AQI was 371 at 10 pm and 376 for the day, remaining very poor overall.

The pollution produced immediate, visible changes in daily life. A thick layer of smog covered several parts of Delhi early Monday and significantly impaired visibility. The Inderlok area was specifically mentioned as one place affected. Reduced visibility made the city look hazy even after celebrations ended.

People also noticed the pollution through smell and breathing discomfort. Social media users reported a strong smell of smoke, reduced visibility and difficulty breathing as fireworks continued through the night. Smoke accumulated over neighborhoods, adding to pollution that was already present before Diwali celebrations intensified.

These effects occurred while Delhi's average AQI settled at 376, in the very poor category. The city had recorded 369 on Saturday, so the average worsened after Diwali. The combination of lingering smoke, poor dispersion and continuing pollution meant that residents faced hazy conditions into Monday morning, with the forecast warning of severe air quality for several days.

Firecrackers worsened air quality because celebrations released additional smoke and particulate matter into an atmosphere already carrying pollution. PM2.5 was Delhi's predominant pollutant on Sunday, and the article states that firecracker emissions added to particulate levels. Smoke then accumulated over neighborhoods as the night progressed.

Restrictions were in place, but fireworks still intensified from around 5-6 pm. Reports came from Pitampura, Burari, Mayur Vihar, Bishambardas Marg and parts of Lutyens' Delhi. The District Magistrate (East) had permitted green firecrackers only on November 7 and 8, during 6-7 am and 8-10 pm.

The result was a sharp nighttime deterioration. At 10 pm, Delhi's overall AQI was 371, and 20 monitoring stations were in the severe category. Burari experienced particularly intense bursting, while residents in several locations said fireworks continued despite the restrictions. Smoke and unfavorable weather then kept pollution near the city.

Firecrackers were only one part of Delhi's pollution problem. The article identifies vehicular emissions, stubble burning in neighboring states and unfavorable meteorological conditions as other contributors. These sources combined with Diwali smoke, increasing the overall pollution burden.

The Decision Support System for Delhi projected that transport would be the largest contributor on Sunday, accounting for 19% of pollution. Stubble burning was expected to contribute 3.5%. The forecast suggested its contribution might remain around 2.99% on Monday. PM2.5 remained the capital's predominant pollutant.

The timing also mattered. Delhi was in the peak stubble-burning season, while low wind speeds and a ventilation index below 6,000 square metres per second hindered dispersion. The Air Quality Early Warning System forecast severe air from November 9 for several days. This means pollution could remain high even after firecracker activity declined.

GRAP Stage III is a higher level of the Graded Response Action Plan, used when air pollution becomes seriously elevated. It signals that authorities must apply stronger pollution-control measures than under lower stages. The article does not list the specific Stage III restrictions, so its exact measures cannot be identified from the provided text.

What the article does establish is that Stage III was already in force across Delhi-NCR when pollution worsened. Delhi's air quality reached 371 at 10 pm on Diwali, and 20 monitoring stations entered the severe category. ITO later recorded 406, while the citywide reading remained very poor at 366 around 7 am.

The timing reflects a rapidly worsening situation involving fireworks, vehicle emissions, stubble burning and poor atmospheric dispersion. The early-warning system forecast severe air from November 9 for several days. Stage III therefore formed the response backdrop, but the article does not say which individual restrictions were imposed or how effectively they were followed.

Wind and ventilation determine how quickly pollutants disperse. When air moves slowly, emissions from vehicles, firecrackers and other sources are not carried away efficiently. A low ventilation index means the atmosphere has limited capacity to dilute and remove pollution from the area.

The article identifies a ventilation index below 6,000 square metres per second, combined with average wind below 10 kilometres per hour, as unfavorable for dispersion. Under these conditions, PM2.5 and other pollutants can accumulate near the ground instead of spreading through a larger volume of air. Smoke therefore remains concentrated around neighborhoods.

This mechanism helped explain Delhi's thick smog and reduced visibility after Diwali. Firecracker smoke was added to transport emissions and other pollution while the atmosphere struggled to clear it. The Air Quality Early Warning System consequently forecast that Delhi's air would enter the severe category from November 9 and remain there for several days.