Delhi has installed a new smog tower, a technological aid to help combat air pollution. Chief Minister Arvind Kejriwal inaugurated the tower behind the Shivaji Stadium Metro station. The structure of the smog tower is 24 m high, which is as high as an 8-storey building. It also has an 18 metre (m) concrete tower with a 6 m high canopy top. There are 40 fans at its base, with ten of them on each side. Each fan is capable of discharging 25 cubic metre per second of air, adding up to 1,000 cubic metres per second for the tower as a whole. There are 5,000 filters inside the tower in two layers. The fans and filters were imported from the United States. Anwar Ali Khan, senior environmental engineer of the Delhi Pollution Control Committee, who was in charge of the project, told the media that the tower uses a downdraft air cleaning system developed by the University of Minnesota. IIT-Bombay consolidated with the American university to replicate the technology, which the commercial arm of Tata Projects Limited has already implemented. At the height of 24 m, the polluted air is sucked in, and the filtered air is released at the bottom of the tower, at the height of about 10 m from the ground. The negative pressure created sucks in air from the top when the fans at the bottom of the tower operate. The filter consists of a 'macro' layer which traps particles of 10 microns and larger, while the 'micro' layer filters smaller particles of around 0.3 microns. The method of downdraft is different from the system used in China. In China, a 60-metre smog tower in Xian city uses an 'updraft' system, where the air is sucked in from near the ground and is pushed upwards by heating and convection, and the air that is filtered is released at the top of the tower. Image Source