Schools have been forced to close as a result
Beijing city authorities have issued a red alert for severe levels of air pollution across the Chinese capital.
The hazardous conditions will last for five days from late Friday until December 21st, Beijing's environmental protection bureau warned on its social media account.
The red alert announcement, which cited an accumulation of air pollution in Beijing and the surrounding areas, means schools will be closed and construction halted across the city.
There will also be traffic restrictions, while citizens will be advised to stay inside.
The colour-graded warning was introduced last year as part of a government initiative to be seen to be taking action on the country's environmental degradation.
Beijing declared its first-ever red alert last December, bringing parts of the capital to a virtual standstill and forcing soldiers on duty in Tiananmen Square to wear smog masks.
The threshold for declaring the highest level of alert has since been raised, and is only issued when the Air Quality Index (AQI) is forecast to exceed 500 for a day, 300 for two consecutive days, or 200 for four days.
According to the World Health Organisation, the maximum safe level for exposure over a 24-hour period is 25.
AQI levels topped 400 for two days earlier this month and an orange alert, the second highest level, was declared in November.
The AQI measures the concentration of tiny particles, known as PM 2.5, per cubic metre.
The particles are particularly dangerous as they are small enough to get into the lungs and in some cases, directly into the bloodstream.
A study published in 2015 found China's air pollution was linked to 1.6 million deaths a year, or 4,000 people a day.
Beijing's air quality ranks among the worst in the world, with much of the blame attributed to industrial pollution and the burning of coal.
Air pollution tends to be more severe in the winter months, when coal-fired central heating systems are in use.
China's government has promised to tackle its environmental problems, and has declared a "war on pollution".