Students hold a HEPA filter as they prepare to put it on a fan at a workshop to learn how to make the DIY air purifier at a college in Beijing October 23, 2014. Smart Air, a company which invented the DIY air filter, said that their DIY device, which combines a basic household fan with a simple HEPA filter can reduce particulate air pollution indoors at low-cost. Awareness of the dangers of Beijing's skies is on the rise, thanks to growing data on its air quality. China will "declare war on pollution," Premier Li Keqiang told parliament in an opening address in 2014. A tougher environmental law took effect on January 1, while a new environment minister took charge on Friday. REUTERS/Kim Kyung-Hoon (CHINA - Tags: POLITICS SOCIETY ENVIRONMENT BUSINESS)

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