Beijing has temporarily shut down 103 heavily polluting factories and taken 30% of government vehicles off the roads to combat dangerously high air pollution.
Air quality in Beijing has mostly stayed above the levels of "very unhealthy" and "hazardous" for about two weeks, Reuters reports.
On Tuesday, it hit 517 on an index maintained by the US Embassy in Beijing, which described the pollution as "Beyond Index".
Beijing's pollution problem has caused widespread public outrage, alarming the ruling Communist Party, which has failed to rein in pollution despite repeated pledges to get tough.
Earlier this month pollution hit a record, 30-45 times above recommended safety levels, blanketing the city in a thick, noxious cloud that grounded flights and forced people indoors.
The emergency measures only last until Thursday.
The government has already announced that it would take 180,000 old vehicles off the roads in Beijing this year and control the "excessive" growth of new car sales in the city.