Beijing said on Monday that it will further strengthen supervision and promote clean energy for heating in an effort to reduce winter air pollution. The announcement came on the same day that public heating systems began trial operations, two weeks before the normal heating time.

Key areas for inspection are heating installations, dust-producing construction sites and coal-burning factories, the municipal environmental protection bureau said.

"In the next two months, random inspections will be conducted to stop illegal outdoor barbecue businesses and burning of leaves," said Mu Liang, head of a monitoring team at the bureau’s municipal environmental monitoring center.

During inspections of 2,033 polluting enterprises in Beijing from Oct 12 to 16, a total of 101 violations were found.

"Apart from coal-burning factories, coal-fired heating systems are another major source of air pollution in winter," said Xie Hongxing, director of the Innovation Centre for Clean-air Solutions, an environmental think tank in Beijing. "Further efforts need to be made to encourage citizens to switch to natural gas and electric systems, especially in rural households and small enterprises."

More ambitious targets for the coming two months have been set.

The year-end target of replacing 1.2 million metric tons of coals with cleaner alternatives in rural areas has been raised to 1.4 million tons, and an estimated of 1.3 million tons of coal will be replaced in urban fringe areas, the bureau said.

The city has witnessed a significant improvement of air quality in the past 10 months. The average concentration of PM2.5 — fine particles that pose particular hazards to human health — was 69.7 micrograms per cubic meter in the city, down 21.8 percent from the same period last year.

The improvement of air quality has to do with air pollution control measures and favorable weather conditions, the bureau said.