A red alert for air pollution is going to take effect starting from this Saturday morning in Beijing.
This is the second time this month that the highest level warning has issued for the Chinese capital.
Emergency measures include an advisory school suspension and a ban on driving vehicles according to their plate numbers.
Outdoor construction activities are ordered to halt and industrial operations will be suspended.
The red alert comes after another round of heavy smog is expected to hit Beijing and its neighboring regions tomorrow and last till Tuesday.
The smog, said to be the heaviest one so far this year, is expected to cut visibility in the city to less than one kilometer.
The density of PM 2.5 pollution in some of the regions will exceed 500 micrograms per cubic mete.
The World Health Organization's recommended maximum is 25 micrograms per cubic meter.
Beijing issued a red alert for heavy air pollution between Dec. 6 and 9, the first time since the emergency response system was created in October 2013.
Coal burning and car emissions are some of the major sources of air pollution. In winter, an increase in coal-burning for heating in north China and still weather often exacerbate other forms of pollution and create periods of heavy smog lasting days.
