Delhi Smog Towers: Solution to Pollution Or Waste of Public Money?

Are anti-smog towers the answer to Delhi’s toxic air emergency? Here’s what we know.

A representative image of an anti-smog tower.

Come next winter, New Delhi will have at least one anti-smog tower to help combat the hazardous air that grips the national capital.

The proposed tower is expected to be built in Central Delhi’s Connaught Place, as a pilot project, within the next 10 months.

An expert panel in November 2019 estimated that Delhi will need a total of 213 anti-smog towers to battle the pollution crisis. It is expected to be constructed along the lines of China’s, which claims to have successfully battled pollution with two such structures in Beijing and Xi’an.

But what is an anti-smog tower? Is it really the answer to Delhi’s toxic air emergency? And will Delhi be able to pull off a Beijing?

The Science Behind Anti-Smog Towers

Imagine an air purifier the size of a skyscraper – there, you have an anti-smog tower. It is nothing but a giant structure fitted with multiple layers of filters, that cleans the air that passes through it.

The 213 towers in Delhi are planned by IIT-Delhi and IIT-Bombay, in partnership with University of Minnesota in the United States, which, incidentally, also helped China install the “world’s largest” the air-purifying tower in Xi’an. The project is at a preliminary stage and will be given the green signal if the pilot is found effective.

Speaking to The Indian Express, an IIT-Bombay professor who is in charge of the project, explained:

“Large-scale air filters will be used in the towers, which will draw in the air through fans installed at the top before passing it through the filters and releasing it near the ground.”

Each tower is expected to be be 20 metres high, just one-fifth of the recently installed air-purifying tower in Xi’an which is 100 meters tall. However, unlike the tower in China which releases clean air from the top of the structure, the one in Delhi is expected to release air from all sides of the 30*30-foot structure.

Experts involved in the project claim that the tower will reduce 50 percent of the particulate matter in an area 1 km in the direction of the wind.

For example, when the tower comes up in Connaught Place, the surrounding area will have cleaner air. Each tower would cost approximately Rs 14 crore, and the pilot is expected to be up and running before next winter, sources told The Quint.

Why Experts Call It ‘Ineffective Band-Aid’

If the entire project with 213 anti-smog towers gets the go-ahead, it would cost over Rs 2,982 crore. Furthermore, if the pilot in Connaught Place is found to be effective after the required studies, then it would mean 10 months each for the construction of the remaining 212 anti-smog towers.

Environmentalists assert that anti-smog towers are ineffective to control pollution and will be a “colossal mistake and waste of public money.”

In an open letter to the Supreme Court, NGO Care for Air’s Karthik Ganesan termed it an “ineffective band-aid,” urging the apex court to withdraw their direction to the governments to formulate an anti-smog towers road-map.

Citing studies, he argued that PM 2.5 can be controlled only by eliminating emissions from the source, not by “purifying air.”

“The air flowing through an indoor space is generally about 100 to 1,000 times greater than what we breathe in the same space. That volume is small enough that one can manage to purify it. The problem is that air flowing through in any outdoor space is generally of the order of 1 million to 1 billion times the air we inhale in the same area. This is why indoor air purifiers work well and outdoor purifiers don’t.”

Karthik Ganesan

Professor of Atmospheric Sciences in IIT-Kanpur, Dr SN Tripathi, also echoed the criticism that the tower will work only a minuscule proportion of the air flowing through the area.

“As a matter of principle, it is difficult to “clean air” like this (using anti-smog towers) because the volume of air in the atmosphere is large. In a 1-km square area, there is a huge volume of air and the purifier will be working only on a minuscule part of it.”

Climate activist PR Vishnu, who recently represented India at the UN Climate Summit, feels there should be focus on eliminating pollutants from the source, like:

  • Strict ban on construction in Delhi-NCR from August, every year
  • Heavy fine on industries that contribute to pollution, especially coal plants. Order their closure during the winter months, if required
  • Pass a strict law at the central government level against stubble-burning in Punjab, Haryana and parts of Uttar Pradesh.

Delhi’s Earlier Experiments With Smog Towers

Delhi’s experiments with anti-smog towers actually started almost a decade ago, in 2010.

The capital was then the fourth-most polluted city in the world, gearing up to host the Commonwealth Games when an Italian company, Systemlife, installed a $300,000 air-filter in Connaught Place.

In the first month of the operation, the company claimed that the purifier collected 2.5 kgs of dust. However, since then, there has been no other number to back that up or even to confirm if the purifier is still working.

According to knowledge platform India AQ, estimates show that Delhi’s particulate matter pollution is approximately 60,000 tons per year. This means 5 million kg per month, and the whole of Delhi would actually need at least 2 million such air purifiers.

Founder-Director of Urban Emissions Dr Sarath Guttikunda, in an opinion piece at that time, noted:

“Installing an air filter in public is more like avoiding the problem and diverting attention away than solving it. Emissions should always be controlled at the source.”

No Lesson to Learn From China’s Smog Towers?

Before 2017, Beijing was the world’s most polluted capital city, not New Delhi. In 2019, the Chinese capital is the 122nd most polluted city in the world, with an average PM 2.5 of below 50.

All thanks to China’s massive cutting down of coal, its rapid switch to renewable energy, its iron-fisted control over factories and industries contributing to pollution, and limitations on the number of vehicles on the roads.

However, the country made headlines for installing the world’s tallest anti-smog tower in 2018. Started in 2015, the project took three years to complete and the government has not revealed the amount spent on it.


While scientists involved in the project claim that the it has brought down PM 2.5 by 19 percent in an area of around 6 sq km, there is no data available to support that it was the air-purifying towers alone that helped reduce the pollution.

Professor of Atmospheric Chemistry Alastair Lewis, at University of York, pointed out the same in a 2018 article:

“A tower that filters the air no doubt will take tiny harmful particles out of the air, titanium oxide paints do react with NOx, and trees do act as sinks for air pollution. However, the more important but often neglected question is whether the effects really make a useful difference.”

Alastair Lewis wrote in 2018

The expedited plan for an anti-smog towers in Delhi was drawn up in just 10 days, after the Supreme Court directed both the central and state government to do so.

But given the gulf of disagreement between the civic authorities and environmental experts on expensive anti-smog towers, perhaps a more thoughtful roll-out is needed… or we could be out thousands of crores of taxpayer money, with still no reduction in hazardous air.