As thick smog choked the capital and many mainland cities for a third straight day, Beijing yesterday issued its first-ever orange fog warning - indicating that visibility was less than 200 metres.
The conditions disrupted air traffic, forced the closure of several highways and sent countless residents scrambling for their surgical masks.
Air-quality readings released by the capital's municipal environmental monitoring centre showed the level of health-threatening PM2.5 particles, or those smaller than 2.5 microns, was 500 in the south of the city, or the upper limit of the scale. In the northern part, the level reached 440, meaning the air quality was a threat to health.
The US embassy's pollution data, published hourly on Twitter, said the PM2.5 level around the embassy was highest at 1pm, when it reached 446, or a "hazardous" level.
Yet the readings still paled in comparison to Saturday's levels, when the PM2.5 reading reached 886 micrograms per cubic metre, according to the embassy's "BeijingAir" Twitter feed.
Meteorologists in the city have forecast that the cloud of haze will linger until Wednesday, when strong winds are expected to blow the pollutants away.
The China National Environmental Monitoring Centre recorded air pollution levels in 33 cities across the country. Changsha , the capital of Hunan , issued a red warning, the highest, as visibility dropped to less than 50 metres.
The heavy smog was responsible for 10 highway closures in five provinces, including Hebei and Liaoning . An accident in Guilin , Guangxi , involved more than 20 vehicles and resulted in one death and 15 injuries. Elsewhere, a high-speed train from Beijing to Wuhan , Hubei , was delayed for more than three hours on Saturday morning because of a technical glitch caused by the smog, Beijing railway officials told China Central Television (CCTV) yesterday.
Airports in Changsha and Kunming closed yesterday morning due to heavy smog, and even though they reopened in the afternoon more than 400 flights were delayed.
For two consecutive days, smog across the nation topped CCTV's 7pm news broadcast. Drivers were even instructed how to travel in smog and the public was advised to buy face masks and to not exercise outdoors.
Duan Lei, a professor at Tsinghua University's School of Environment, said: "The major problem with Beijing's air quality comes from car exhausts. It is the government's responsibility to foresee the consequences and control the number of cars on the road. Beijing still has too many cars on the road even with the restrictions on purchases and driving."
The Beijing Municipal Education Commission on Saturday issued an urgent order that primary and middle schools in heavy pollution areas were to hold physical education lessons indoors. More than 30,000 factories that release gases into the air were told to discharge less and government cars were ordered to stay off the roads.
Residents could do little aside from searching for facial masks and limiting outdoor activities. "People are forced to stay at home due to the bad air quality, not because of war or hostile foreign forces, but because of incompetent administrators in the country and the blood-stained GDP," said a Sina microblog user.