The Delhi government plans to install 150 outdoor purifiers at Nehru Park to filter out PM2.5. Last month, Delhi environment minister Manjinder Singh Sirsa announced that the decision was based on “successful” trials in four locations in the city.
An analysis of such purifiers, however, reveals they are barely helpful.
The New Delhi Municipal Council had earlier installed air purifiers at four other locations on a trial basis – in Anand Vihar ISBT in 2023, at the Ambassador Hotel in Khan Market, and New Moti Bagh in 2024, and Jangpura in January 2025. The BJP government in Delhi now proposes to install at least 150 air purifiers, at an estimated cost of around Rs 7.5 crore, according to an official who spoke to Hindustan Times.
While officials told The Indian Express that the PM concentration at Anand Vihar ISBT had reduced by 30 percent in a 4,500 sqm radius, data from the nearest air monitoring stations of these locations revealed that the air purifiers had little larger impact, even if they might have reduced the concentration of particulate matter within a certain smaller radius.
Anand Vihar and Ambassador Hotel
Officials told The Indian Express that 10 air purifiers were installed at ISBT-Anand Vihar in 2023, with each covering a 1 sq km area. A performance report, the officials claimed, pegged the purifiers’ efficiency at 85 percent. But data from the Central Pollution Control Board (CPCB) from the nearest monitoring station – Anand Vihar – showed that PM2.5 levels worsened in the years after the purifiers were installed.
In 2022, the year before the purifiers were installed, the annual PM2.5 average was 124.2 µg/m³ (micrograms per cubic metre). In 2023, when the purifiers were installed, the PM2.5 average increased to 127.8, and in 2024, it further rose to 136. (Averages exclude 10 days in 2023 and 22 days in 2024. Data for these days was not available on the Central Pollution Control Board website.)
According to WHO standards, the annual average concentration of PM2.5 should not exceed 5, while the 24-hour average exposure should not exceed 15. The CPCB’s National Ambient Air Quality Standards (NAAQS) recommend that the annual average PM2.5 concentration should not exceed 40, and the 24-hour average should not exceed 60.
In Anand Vihar, the PM2.5 annual average exceeded the NAAQS both before and after the installation of air purifiers.
The area is one of Delhi’s 13 pollution hotspots and recorded ‘severe’ AQI (401-500) for 33 days in October-December 2024. In 2021, an 80-foot smog tower worth Rs 13.6 crore was installed in Anand Vihar. In 2023, a senior DPCC scientist told the National Green Tribunal that the tower’s effect was too small to make a difference in the air quality of the surrounding areas.
Air purifiers were installed near the Ambassador Hotel in 2024 when the average annual PM2.5 at the nearest air-monitoring station – Lodhi Road, IMD – was recorded at 79 µg/m³. This was an increase from the previous year, when it was 75.9.
In New Moti Bagh and Jangpura
Before the installation of air purifiers at New Moti Bagh in 2023, the annual average concentration of PM2.5 in the area was 120.2 µg/m³, according to data from the nearest monitoring station at RK Puram. In 2024, the year when purifiers were installed, the level nominally dropped to 118.3.
(Averages exclude six days in 2023 and two days in 2024 for which data was not available on the CPCB website.)
Manoj Kumar, a researcher at the Centre for Research on Energy and Clean Air (CREA) and one of the experts guiding Newslaundry’s Fight To Breathe campaign to tackle air pollution, says that air purifiers do not reduce ambient air pollution in any way. Meteorological factors such as high wind speed and direction as well as factors like boundary layer height contribute to the dip in PM2.5 levels. Such factors likely led to a dip in the RK Puram air monitoring station in 2024, he said.
In Jangpura, air purifiers were installed in January 2025. In 2024, the annual average concentration of PM2.5 was 85.3 µg/m³ at the nearest air monitoring station, the Jawaharlal Nehru Stadium, while the 2025 average was 65.4 until July 6.
The annual average concentration of PM2.5 is likely to increase during winter months, when pollution peaks in the city.
‘Need to cut emissions at the source’
Similar short-term measures – smog towers, sprinklers, triggering artificial rain through cloud seeding, refuel ban on end-of-life vehicles – have drawn criticism from researchers, who have been calling for cutting emissions at the source, which includes vehicular emissions, industrial sources, biomass cooking, and transboundary emissions.
Jai Dhar Gupta, the founder of Nirvana Being, a brand that specialises in clean air solutions, compares the purifiers to smog towers. “It doesn't matter how many of these machines [smog towers and air purifiers] you set up in parks and every nook and corner of every street; it's not going to solve the problem. Delhi’s airshed is vast, and that volume of air cannot be cleaned by any number of machines. Air purifiers can clean micro-environments because there is a finite amount of air. And that’s why we sell air purifiers of different sizes. If the room is of X size, we know the volume of air, and then we suggest a machine that’s appropriate for that size of room based on the air changes and the number of times that air will pass through that machine in an hour. In ambient air, it’s impossible.”
For Nehru Park, Sirsa said that the government would not be spending any money as this is going to be a CSR initiative and that the responsibility for implementing the project will be given to two or three companies.
But experts warn against this. Kumar says, “Even if it’s CSR, be meaningful. No scientific community will approve of these installations. They should invest in other meaningful measures of cutting the emissions at the source.”
This report is part of a collaborative campaign to tackle air pollution. Here’s how you can join the Fight To Breathe. Click here to power this campaign.
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