Heavy pollution peaked on Monday in the region around Beijing in northern China but is expected to be dispersed by a cold front on Tuesday night.
The air quality index (AQI) reached 201 at 10 am in Beijing, suggesting heavy air pollution, according to statistics provided by the Ministry of Environmental Protection (MEP).
The Global Times observed many people wearing masks on the streets in the capital.
A resident in Chaoyang district told the Global Times that she had barely opened the windows in the last few days and has been using an air purifier in her bedroom.
From Saturday to Wednesday, severe air pollution swept the Beijing-Tianjin-Hebei region and nearby provinces, according to a notice the MEP sent to the Global Times on Thursday.
The National Meteorological Center (NMC) on Sunday issued a yellow alert for heavy fog in northern, eastern and southwestern China, including Beijing. In some of those regions, visibility may fall below 200 meters, the Xinhua News Agency reported.
The NMC suggested that residents take precautions to ensure traffic safety.
China has a four-tier color-coded warning system for severe weather, with red being the most serious, followed by orange, yellow and blue.
Meanwhile, a cold front will sweep across northern China in the next three days, bringing falling temperatures, rain and snow, the national observatory said Saturday, according to Xinhua.
The cold front is expected to disperse the pollution from Tuesday, the NMC predicted.
Air quality usually worsens in late autumn and winter in northern China due in part to less wind and increased emissions from heating sources. Aside from enforcing rigorous environmental regulations, authorities are speeding up research into the causes of smog to find effective solutions, according to Xinhua.
Tianjin in North China has closed 9,081 heavily-polluting companies this year, according to the municipal environmental protection bureau. The companies are among nearly 19,000 that were found to have violated policies related to environmental protection, land use and construction during inspections in 2017, Xinhua reported on Monday.