Delhi AQI falls to ‘poor’ ahead of Diwali, likely to deteriorate further this week — pollution-control curbs kick in

An AQI of 261 means Delhi’s 24-hour average air quality was in the “poor” category. The CPCB scale places good air at 0–50, satisfactory at 51–100, moderate at 101–200, poor at 201–300, very poor at 301–400, and severe at 401–500. The category signals how polluted the air is, not just the temperature or visibility.

Delhi’s reading was therefore worse than moderate, which ended at 200. It was also 40 points below the threshold for very poor air. The distinction matters because each higher band reflects a heavier pollution load and a more difficult winter environment for the city.

The reading was expected to worsen. The AQEWS forecast poor air on Monday and Tuesday, with possible deterioration to very poor by Wednesday. Its six-day outlook remained poor to very poor.

Delhi’s 24-hour average AQI rose from 117, classified as moderate, to 261, classified as poor. That was an increase of more than 144 points in a day. The sharp change shows how quickly winter conditions can reverse the improvement that followed last week’s rains.

Pollution was not confined to one location. On Sunday, the Sameer app recorded an AQI of 277. Among 54 monitoring stations, 18 reported poor air and 25 reported very poor air. Together, those readings show that most reporting stations were already in the two worst categories mentioned in the city’s forecast.

Local conditions were also severe. The area around ITO recorded an AQI of 349 on Monday morning, placing it in the very poor category. The AQEWS expected poor air on Monday and Tuesday, followed by possible deterioration to very poor.

Delhi’s air worsened because colder, foggy and calm conditions slowed the movement of pollutants away from the surface. Instead of dispersing through the atmosphere, emissions remained concentrated near the ground, where people live and travel. This helps explain why the improvement after last week’s rains quickly disappeared.

The minimum temperature on 1 November was 18℃, 1.9 degrees below the seasonal average. Meteorologist Navdeep Dahiya said winds were coming from the northwest under calm conditions, so emissions would persist for longer. The article also describes fog as a condition that traps pollution near the surface.

These conditions support the beginning of the smog season. Dahiya said most Delhi NCR sensors were already above AQI 300, with many rising toward 400–500. With Diwali less than a week away, the article expected air quality to worsen further in the following days.

Delhi’s smog comes from several sources rather than one activity. The article identifies traffic, NCR industries, dust, coal and fuel emissions, and farm fires. Pollution can also arrive from outside Delhi, making the city’s air quality depend on the wider airshed and regional conditions.

Stubble burning’s estimated contribution rose sharply to 18.57% on Sunday, from 5.33% on Saturday, according to the Decision Support System. Jinitha Varghese said two-thirds of Delhi’s fine particles came from outside the city, while Delhi’s own traffic remained its largest single source. The article also notes that farm-fire contributions typically peak in early November.

The mix may become more difficult to control as winter progresses. The article says about 40% of particles form in the air from gases released in the airshed. Therefore, smoke from coal, fuels and stubble can become secondary pollution, which is easy to undercount.

A move from poor to very poor would mean Delhi was entering a higher pollution band, with more polluted air remaining around the city. The article does not quantify specific health effects, but the worsening category matters because residents would face more severe air conditions during the winter smog season. It also signals a need for stronger controls.

Daily life could become less convenient. Vehicles queued at Delhi’s borders for checks when the new restrictions began, causing heavy traffic snarls. Dust-generating outdoor construction was banned, parking charges doubled, and physical attendance in government and private offices was capped at 50 percent.

The outlook already pointed downward. AQEWS forecast poor air on Monday and Tuesday, with possible very poor air by Wednesday and poor-to-very-poor conditions over the next six days. If that forecast materialises, travel delays and activity restrictions could continue through the winter-control period.

Delhi introduced special winter measures to reduce pollution and traffic congestion. They include restrictions on certain vehicles registered outside Delhi, a ban on dust-generating outdoor construction, doubled parking charges, and a 50 percent cap on physical attendance in government and private offices. The measures apply for varying periods from 1 November to 28 February.

The vehicle restrictions target outside-Delhi vehicles that do not meet applicable emission standards, including those conforming to BS-IV or older standards. The article states that BS-VI, CNG and electric vehicles are allowed, subject to applicable exemptions. Construction controls directly target dust, while parking and office measures aim to reduce traffic and travel.

The expected mechanism is straightforward: fewer higher-emitting vehicles, less dust-generating work, and less commuting can reduce emissions and congestion. Implementation was not frictionless. Border checks caused heavy traffic snarls on the first day, even as Delhi’s air quality deteriorated.

Fine particles in Delhi’s smog come from direct emissions and from gases that form particles after entering the atmosphere. This “secondary” pollution can originate from coal, fuels and stubble smoke. Because the particles form in the air, measuring only visible or directly emitted pollution can miss part of the total load.

The article says about 40% of particles form in the air from gases released in the airshed. It also says two-thirds of Delhi’s fine particles come from outside the city, including NCR industries and traffic. Delhi’s own traffic remains its largest single source, showing that local and regional emissions overlap.

Weather determines how long this pollution remains concentrated. Low temperatures, fog and calm winds slow dispersal and trap pollutants near the surface. As farm-fire contributions typically peak in the first week of November, regional pollution may continue adding to Delhi’s smog as winter conditions strengthen.