Delhi-NCR saw improved air quality in early 2025 due to favourable weather. After Diwali, AQI surged, making Delhi the most polluted major city globally. Data from CPCB and IQAir highlighted drastic AQI increases, with residential and industrial areas worst hit. Can green crackers help?

From Oct 20 onward, ozone and CO disappeared from the AQI charts, replaced by particulate matter – tiny, hazardous particles that penetrate deep into the lungs.

Source apportionment data from the Decision Support System (DSS) for air quality management shows that the mix of pollution sources impacting Delhi has changed since Diwali on October 20.

Delhi’s air quality stayed in the “very poor” range two days after Diwali, with an AQI of 353. Data from the Decision Support System showed that over 36% of the pollution came from “unaccounted sources”, meaning emissions not clearly identified or tracked. Transport, industry, and waste burning also added to the problem. Sunil Dahiya from Envirocatalysts explained that these unaccounted sources likely include power plants, industries, and crop burning in nearby states, which are not properly captured in pollution records.

A reading of 351 qualifies as “very poor” – a category for which NCDC recommends “avoiding physical activity outdoors” and remaining indoors as far as possible

An analysis of CPCB and DPCC data by HT revealed that only nine stations – barely 23% of the city’s monitoring network – recorded continuous data

Several air quality monitoring stations in Delhi, including RK Puram, went offline for hours on Diwali night, leaving critical PM2.5 data missing during peak pollution hours. Experts said the data gaps skewed average readings and hindered analysis of pollution sources. Sunil Dahiya, founder of EnviroCatalysts, said missing data hampers understanding of pollution trends and called for improved data transparency and monitoring practices.

Several government-run open-access websites that publish real time monitoring of air quality were unavailable for several hours during peak firecracker time on Diwali day

Firecracker emissions contributed between 30% and 40% to Delhi’s pollution on Diwali, with PM2.5 levels spiking eightfold due to stagnant wind conditions. Experts said calm weather and poor dispersion worsened air quality overnight, pushing pollution levels 60–67 times above WHO’s safe limit. Data analysis by EnviroCatalysts revealed that PM2.5 levels on Diwali night have consistently surged 200–300% compared to pre-Diwali levels since 2021.

The report has revealed that a significant failure occurred as 30 of Delhi's 39 official air quality monitors were offline during the Diwali period, hiding the true scale of the pollution crisis from the public.

Delhi's air monitoring stations missed key pollution data during Diwali's toxic air spike.

On Diwali night, Gurgaon’s PM2.5 levels soared to 16 times the national limit as residents continued bursting crackers well past the Supreme Court’s permitted 8–10 pm window. The hourly concentration of PM2.5—a fine particulate pollutant linked to respiratory problems—rose sharply, with Sector 51 recording the highest at 949 micrograms per cubic metre around midnight. Despite restrictions, fireworks continued sporadically till 2 am in several neighbourhoods, including DLF phases, Sector 56, Palam Vihar, and Golf Course Extension. Residents complained that noise and smoke lingered for hours, reducing visibility. Officials said the city’s air quality remained in the ‘severe’ category for several days after Diwali.

Vaani Kapoor is currently in Delhi to celebrate Diwali with her family. The actress on Tuesday took to Instagram to share that she woke up to Delhi's AQI touching 447, and she has urged people to celebrate the festival without dimming the air quality. Read on to know more...

It was a noisy Diwali in Delhi as ‘green’ fireworks burst non-stop across the capital. Now it sits under a thick, choking blanket of smog filled with ultra-fine pollutants. According to data, the average AQI touched the ‘severe’ category, at 451, at 7 am on Tuesday, 1.8x above the national average

Gurgaon is expected to witness dense haze following Diwali as weather conditions turn unfavourable for pollutant dispersion. According to the IMD, wind speeds will drop below 8 kmph, and calm conditions may trap smoke, causing AQI levels to deteriorate sharply after the festival.

रोहतक में दिवाली से पहले वायु गुणवत्ता सूचकांक (एक्यूआई) बढ़कर 290 तक पहुंच गया है, जिससे हवा 'बहुत खराब' श्रेणी में आ गई है। प्रशासन ने ग्रेप-2 के नियम लागू करते हुए सड़कों पर पानी का छिड़काव और सफाई अभियान शुरू किया है।

The deteri­or­a­tion in Delhi’s air qual­ity, which was skirt­ing the “very poor” cat­egory on Sunday, was caused more by external factors than from sources within the cap­ital, accord­ing to the Centre’s Decision Sup­port Sys­tem (DSS). Data on Sunday showed at least 67.89% of Delhi’s total PM2.5 con­tri­bu­tion was from external sources.

The deterioration in Delhi’s air quality, which was skirting the ‘very poor’ category on Sunday, was caused more by external factors than by sources within the capital, according to the Centre’s Decision Support System (DSS).
Data on Sunday showed that at least 67.89% of Delhi’s total PM2.5 contribution was from external sources.
For the sources within Delhi, the transport sector in Delhi accounted for 16.43% of the pollution in the city, followed by Delhi’s residential sector (4.27%) and then the industries sector (3.63%).

Studies have previously shown that the city’s particulate matter levels spike sharply in the days leading up to and during Diwali

City’s pollution worsens even before the festival, with Anand Vihar’s AQI hitting 384 (“very poor”) and several areas crossing 200