A man pedals a bicycle connected to an air purification system inside a dome called the "Eco Air Bubble" during the Smart City 2013 International Design Exhibition in Beijing October 11, 2013. The installation uses a human-powered air purification system combined with green plants generating fresh air and has a digital display showing the real time difference of air quality of PM 2.5 between the interiors and exteriors of the installation. The exhibition lasts till October 13. REUTERS/Kim Kyung-Hoon (CHINA - Tags: SOCIETY ENVIRONMENT)