The 60 m high chimney contains particle filters and is powered by solar energy. It was developed by the group of Junji CAO at CAS Key Laboratory of Aersol Chemistry and Physics. The concrete chimney sits atop a large open structure with a glass roof. Solar radiation hitting the glass heats the air, causing it to rise towards the base of the tower. The air then passes through a wall of industrial filters before billowing out the chimney. The system is inspired by renewable-energy power plants that generate electricity from solar heat. At the tower and at 10 monitoring stations across a 10 square-kilometre area, monitors measure particulate matter under 2.5 micrometres in diameter (PM2.5). In a test run this winter, it was found that the tower expels between 5 and 8 million cubic metres of filtered air a day. The surrounding air monitors registered a 19% decrease in PM2.5 concentrations compared with monitors in other parts of the city. Sulfur dioxide gas, nitrogen oxides and ozone were not measured.

CAS news release, March 12, 2018