Recently the air pollution in Beijing has become a world wide topic. Just two weeks ago, Beijing has recorded the worst pollution days in 20 years. Air Quality Index shot through the roof and the government issue warning to ask the public stay at home. aqicn.info stands for Air-Quality-Index-China, which is a very useful site providing live data of air quality index in China and some parts of Asia.
If you are travelling to China, quickly check this site for the latest AQI report of your destination. Better to be prepared.