Delhi is one of the most polluted cities in the world. PM2.5 pollution levels reach more than 10 times the World Health Organization’s annual limit. To combat air pollution, the Delhi government recently installed a new smog tower in the center of the city. But will this Delhi smog tower have an effect on reducing outdoor air pollution?
How the Delhi Smog Tower Works
The Delhi smog tower is 24 meters tall and includes 40 large fans. The air is sucked in from the top and the filtered air comes out from the bottle of the tower. The tower consists of 10,000 filters to filter out particle sizes up to 0.3 microns.
The Delhi government claims that this smog tower can deliver clean air up to one thousand cubic meters per second. It also uses 8 sensors to measure the air quality before and after filtration.
Will the Delhi Smog Tower Work?
This isn’t the first outdoor air purification project. Similar smog towers were installed in Connaught Place, Delhi, and Xian, China. Data on the effectiveness of these “smog towers” was not promising.
Dutch artist Daan Roosegaarde built an ionizing tower in Beijing and Tianjin, claiming it would clean the outdoor air. Independent tests found the air filter tower was not providing clean air even within 10 meters of the tower. Even a careful look at the team’s own modeling estimated only a 20% drop among large particles (PM10, not PM2.5), assuming zero wind, and only up to 20 meters from the tower. Thus, the tower was more art than science.
Real-Data: Effectiveness of Outdoor Air Purifiers
To understand the effectiveness of an air purifier in an outdoor setting, the CEEW team carried out a real-world test using Smart Air’s Blast Mini/Ladakh Mini air purifier. With a CADR of 585 m3/h, the purifier cleans significantly more air than the typical home air purifier. During this real-life test, two air quality sensors were used to measure the PM2.5 levels at varying distances of 2 feet, 4 feet, and up to 12 feet from the air purifier.
Image Courtesy: CEEW
At the beginning of the test, the outdoor PM level was 89 ug/m3. Then we turned on the air purifier for 1.5 hours. After this, we measured air quality at different distances to determine the effectiveness of the air purifier in an outdoor environment.
We first measured at a distance of 4 feet in the line of airflow. This reduced pollution levels to 51-53 ug/m3. Next, at a distance of 12 feet, the PM 2.5 level was reduced to 62-64 ug/m3. Towards the end of the experiment, we turned the air purifier off and the PM2.5 levels reached ambient levels immediately.
In 2020, Delhi’s annual PM 2.5 concentration was 89 ug/m3 and it’s highly unlikely that installing these smog towers would have any significant effect on Delhi PM2.5 levels.
The best way to reduce air pollution is to curb emissions at the source. This would require a systematic approach and collective efforts both at the government level and citizen level. More pollution control equipment in power plants and industries with heavy penalties for breaching the air pollution laws are needed. The government should improve public transportation and electric vehicles in tier-2 and tier-3 cities to reduce air pollution across India.
Studies Document Protective Effects of Purifiers, Masks
Despite the harms of PM2.5, studies have found that wearing masks prevents harmful effects on blood pressure and heart rate variability. Similarly, placebo-controlled studies of air purifiers have found that reducing particulate in the home prevents harm to blood pressure, inflammation, and immune response—even among young, healthy twenty-year-olds.
How I Protect Myself
Smart Air is a certified B Corp committed to combating the myths big companies use to artificially inflate the price of clean air. To help people living in polluted cities protect themselves, Smart Air provides empirically backed, no-nonsense purifiers and masks, thereby helping to lower the cost of clean air.
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