The capital’s Environmental Protection Bureau issued a blue alert for air pollution on Thursday afternoon, forecasting an air quality index of between 200 and 300 for at least a day.
Visibility dropped to below 500 metres in some areas of the city as the pollution mixed with heavy fog.
At 9am, the capital recorded an average air quality index of 277 with some areas reaching almost 350, according to monitoring data from the United States Embassy in Beijing.
The smog blanketed not only Beijing but also some parts of Liaoning and Shandong provinces and was expected to continue through Saturday.
The poor air quality is expected to improve gradually to “slightly polluted”, or an AQI of between 100 and 150, on Saturday when it is forecast to rain, but will only change to “good”, or an AQI of between 50 and 100, on Monday.
Wang Buying, an engineer with the Beijing Municipal Environmental Monitoring Centre, told Xinhua that Beijing was more likely to experience temperature inversion, or temperature rising with height, in September and October when the weather is usually stable with little rain, which makes it very difficult for pollutants to disperse.
No disruption to flights has been reported at Beijing Capital International Airport.