A blanket of humid, still air resulting in smog that is expected to shroud Beijing for at least three days triggered the capital's first ever pollution red alert on Tuesday.
Schools closed and rush-hour roads were much quieter than normal as the alert closed many factories and imposed restrictions to keep half the city's vehicles off the roads.
The alert in effect through Thursday — the most serious warning on a four-tier system adopted in 2013 — means authorities have forecast three consecutive days of severe smog.
Despite some improvement in Beijing's air over the past year, readings of dangerous particles Tuesday were as high as a dozen times the safe level, in what has become an embarrassment for a government that has made a priority of cleaning up the legacy of pollution left from years of economic growth.
The alert coincided with global climate change talks in Paris, where Chinese President Xi Jinping has vowed action on greenhouse gas emissions. It's the second time this month that Beijing has experienced a prolonged bout of smog. Beijing was also shrouded in persistent smog for most of November, when power demand soared because of unusually cold weather.
Under the current red alert, schools were advised to voluntarily close unless they had good air filtration systems. However, Beijing's education commission later issued a separate order for all schools to close through Thursday.
By late morning on Tuesday, the U.S. Embassy's monitoring station which many residents rely on for accurate readings. recorded an air quality in the "unhealthy" range.
Readings of PM2.5 particles climbed above 300 micrograms per cubic meter in some parts of the city Tuesday and were expected to continue rising before the air begins to improve with the arrival of a cold front on Thursday. The World Health Organization designates the safe level for the tiny, poisonous particles at 25.
Along with limiting cars to driving every other day depending on the last number of their license plate, a raft of other restrictions will seek to reduce the amount of dust and other particulate matter in the city of 22.5 million people. Officials said extra subway trains and buses would be added to handle the additional strain on public transport.
City residents reacted with a mix of alarm and nonchalance: "This is modern life for Beijing people. We wanted to develop, and now we pay the price," Beijing office worker Cao Yong said during a break from work.
"You have to do whatever you can to protect yourself," Beijing resident Li Huiwen said while stopping at a market. "Even when wearing the mask, I feel uncomfortable and don't have any energy."
A man who gave only his surname, Du, said the haze was good for taking photographs of old buildings and that he was taking advantage of a lack of crowds near Beijing's ancient Forbidden City. "I like this kind of haziness. It gives a blurry feeling and makes you feel like you're in a dream."
"You live in Beijing, you just get used to it. Every winter is like this," said a store clerk who gave only her surname, Sun, and who said the restrictions were a nuisance. "But now that they're cancelling school it becomes really inconvenient. If you don't get time off from work, who watches the kid?”
Polluted air throughout broad swaths of China has had severe health effects. A study led by atmospheric chemist Jos Lelieveld of Germany's Max Planck Institute and published this year in Nature magazine estimated that 1.4 million people each year die prematurely because of pollution in China.
Another study found that women who were in Beijing and pregnant during the 2008 Beijing Olympics — when officials strictly controlled air pollution — gave birth to heavier babies than in years when the city was smoggier.
Most of the pollution is blamed on coal-fired power plants, along with vehicle emissions and construction and factory work. China, the world's biggest carbon emitter, plans to upgrade coal power plants over the next five years to tackle the problem, and says its emissions will peak by around 2030 before starting to decline.
While emissions standards have been tightened and heavy investments made in solar, wind and other renewable energy, China still depends on coal for more than 60 percent of its power.
Al Jazeera with wire services