China's capital Beijing issued its second smog red alert of the month on Friday, triggering vehicle restrictions and forcing schools to close.
A wave of smog is due to settle over the city of 22.5 million from Saturday to Tuesday. Levels of PM2.5, the smallest and deadliest airborne particles, are set to top 500, according to the official Beijing government website.
That is more than 20 times the level that is considered safe by the World Health Organization.
Half the city's cars will be forced off the road on any given day, while barbecue grills and other outdoor smoke sources will be banned and factory production restricted. Schools will close and residents advised to avoid outdoor activities.