A stagnant weather pattern combined with high levels of factory pollution and car exhaust has led to extremely dangerous air quality levels for one of the world's most populated cities.
Shanghai, home to more than 23 million people, was forced to take action on Friday as the concentration of harmful PM 2.5 particles reached 602.5 micrograms per cubic meter, according to the Associated Press.
This level well exceeds the World Health Organizations safety guideline set at 25 micrograms.
In reaction to these high levels of air pollution, schools were closed and children were told to stay indoors. The city also halted construction projects and reduced the number of government vehicles on the road.
The air quality level reached on Friday is the highest since the city began recording the data in December 2012.
A large area of high pressure centered over the city is leading to a stagnant air mass over the region allowing the air pollution to build up.
No changes in the weather pattern are expected through Sunday, likely leading to continued dangerous smog for Shanghai and surrounding areas.
A cold front will then press through the region on Monday leading to an increase winds throughout the atmosphere which should help reduce pollution levels.