Ever since coal-burning heating systems were fired up in mid-October, residents in Harbin, Heilongjiang province, have suffered from virtually constant smog, arousing queries about what the government is doing about it.

On Tuesday morning, the city's meteorological authorities upgraded the yellow alert for smog to orange, the second-highest level in the nation's four-tier emergency response system.

The air quality index in the city hit 500 from Monday evening to early Tuesday, according to the National Environmental Monitoring Center. Anything above 300 is considered hazardous.

"In fact, we have promoted a series of measures to control air pollution this year," Yao Weijing, deputy director of Harbin's environmental protection bureau, said on Tuesday. "For example, we phased out about 2,000 small coal-fired boilers, accounting for about 98 percent of the city, which can help reduce 20,000 metric tons of dust emissions and 2.4 million tons of coal burned per year.

"However, the recent meteorological conditions don't help dissipate the airborne particles. The burning of crop stalks has become another important factor."

On Saturday, a framework agreement for joint efforts against air pollution was signed by Harbin, Suihua and Daqing. Under the agreement, a super lab to monitor haze will be built in Harbin, which will share data with Suihua and Daqing.

Compared with current methods, which can only monitor six indexes, a super lab can monitor more than 100 and conduct in-depth analyses of pollution causes.

The agreement also promotes the goal of seeing air quality in each of the three cities much improved by 2018.

"When I got up, I noticed the strong smell of smog pervading the air in the room," said Du Shangda, father of a seventh-grader in Harbin. "I told my daughter to stay indoors and to drink more water."

"To avoid inconvenience for residents, we didn't adopt traffic controls. But beyond that we are taking all the measures associated with a red alert," the environmental protection bureau's Yao said. "Kindergartens and schools will cancel outside activities or discharge students early."

During the red alert, cars will be allowed on the roads according to license plate number - odd or even to match the date - and enterprises and public institutions will adopt flexible working hours.

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