Beijing has issued an orange air pollution alert, the second highest possible warning. Dense smog has covered much of the capital, and is expected to last for three more days. This marks the first pollution warning since the city launched an emergency response plan in October last year.

Beijing has a four-level alert system, which uses the colors blue, yellow, orange and red to indicate the level of air pollution. Under the orange alert, industrial plants have to close or reduce 30 percent of their emissions. Fireworks and outdoor barbecues are also banned across the city.

If a red pollution alert is issued, traffic is cut, with alternate driving days handed for even and odd-numbered license plates. This also affects government cars, with 30 percent of them required to stay off the roads. Meanwhile, kindergartens, primary and middle schools are advised to suspend classes.