Beijing's 17 million resident can drive, construct and manufacture … until Sunday.
But then, construction stops, factories shut down and half the cars will be banned every day until after the Olympics, CBS News correspondent Barry Petersen reports.
Call it D-Day in a $16 billion battle against air pollution.
"Is the air going to be clean?" Petersen asked at a news conference.
The answer he got from the environmental bureau, translated into English: "It will be safe … everyone can be at ease."
Confidence that comes from perhaps the world's most sophisticated computer system for watching - and if, need be, trying to change - Mother Nature.
Tracking pollution from as far away as India, focusing heavily on surrounding provinces and their big polluters.
At one steel plant 300 miles from Beijing, the boss is more than ready to shut the plant down if high winds start blowing this faraway pollution into Beijing where it can get trapped by mountains. Then, the only solution is rain.
And they'll try that, too - firing artillery shells into the sky filled with a chemical thought to trigger rain showers.
But even if China says it's a good air quality day - there are doubters.
Some pollution monitors were moved to the suburbs, where cleaner air can skew daily results and make the overall polution numbers look better.
And then there is one thing no man can control - the weather.
"My prayers are with the Chinese," said pollution expert Professor Jay Turner. "We could just experience a weather episode that is so conducive to high air-pollution levels that the air quality could be bad under those conditions."
Athletes like Australian marathoner Lee Troop know they're taking a chance.
"If I knew the day after I raced in the Olympic Games I would have long-term ... complications from running in the Olympic Marathon, I would still run," Troop said.
So athletes with gold on their mind, and China with its reputation in mind, will simply have to hold their breath - and trust in the skies.