At a park in one of the world’s most polluted cities, a sleek filtration “tower” has been quietly purifying the surrounding air since last summer. Dubbed Verto, the 5.5-meter-tall (18-foot) device reduces levels of nitrogen dioxide and dangerous fine particles in New Delhi’s Sunder Nursery by filtering 600,000 cubic meters of air a day — which is equivalent to the volume of 273 hot air balloons. Now, having collected data from their prototype, the architects behind the invention believe their project can be scaled up to clean big public spaces, neighborhoods and even entire cities. Designed by architecture firm Studio Symbiosis, which has offices in India and Germany, the towers contain five air filtration “cubes” stacked inside a geometric shell. The firm’s husband-and-wife co-founders, Amit and Britta Knobel Gupta, say their fan-powered devices can clean air within a radius of 200 to 500 meters (656 to 1,640 feet) in enclosed spaces, though outdoors this distance would be 100 to 350 meters (328 to 1,148 feet), depending on wind speed and how open the surroundings are. “Now that (findings from the prototype) are what we expected, we will start speaking to the government authorities about further installation,” Amit said on a video call from New Delhi, revealing that the firm has also spoken to potential buyers in countries from Uzbekistan to France and New Zealand. Studio Symbiosis said that a construction company in the US is considering ordering around 40 of the towers to tackle dust and fine debris at building sites. “I think (they could also be installed) in public parks and public plazas, where people spend quality outdoor time,” Britta said, adding that installing the towers in spots where homeless people sleep might also be “very beneficial.” Deriving its name from the Latin word “vertente,” or “to turn,” Verto’s twisting form was designed to push as much air as possible across the device’s surface, where it is sucked into filters and expelled. Using filters from German firm Mann+Hummel, the Studio Symbiosis architects focused on creating the most efficient shape for the towers, with digital models simulating different wind conditions. “It’s all about wind velocity, so we looked at jets — and how their propeller engines work — as well as car spoilers,” Amit said, explaining how small adjustments made the towers more aerodynamic. “It was a back-and-forth process, in terms of trying to get the optimum shape that would increase the wind speed and the surface area.” Designed as ‘a mass product’ In 2019 alone, air pollution is thought to have caused nearly 1.6 million deaths in India, according to a study in medical journal The Lancet. New Delhi is regularly shrouded in smog, with vehicle emissions, crop-burning and coal-fired power plants all contributing to the city’s declining air quality. The US-based Health Effects Institute last year named India’s capital as the city with the highest exposure to fine particulate matter, or PM2.5, in the world. And in addition to the direct impact of pollution, the resulting climate change has caused heat waves that have killed more than 24,000 people in the country since 1992, according to a study published by the University of Cambridge last month. The Guptas say they were prompted to act by their own negative experiences of pollution after moving to New Delhi from London. “Our core business is architecture — we did not want to get into air purification,” Amit said. “But the pollution here was just not acceptable. It’s very bad.” Ironically, by using electric fans to suck in air, the towers are contributing — albeit negligibly — to the very emissions they are trying to mitigate. To reduce Verto’s environmental impact, Studio Symbiosis installed energy-efficient “smart” fans that vary according to local conditions (slowing down when pollution is low, or when strong winds provide natural airflow). The architects claim that each tower consumes power at the same rate as an industrial vacuum cleaner “but with 100 times the airflow.” The filters, which need to be changed every three to nine months, are partly recyclable, they added. Noise generated by the towers is, at a maximum of 75 decibels, similar to that of a standard kitchen blender. Amit estimated that “maybe 100” of the towers would be required to filter air across central New Delhi, though he said further research and a “full-scale model” would be required to calculate more accurate figures. The devices, which are made from glass fiber reinforced concrete, are also designed to be easily assembled and transported, with the hope they can be adopted at scale. “They’re made from repeating modules, so we don’t need so many molds and we can flat-pack them and ship them,” said Britta. “The idea is to make this a mass product,” Amit added.