A coal-fire stove provided heating for Zhao Yaoqin's courtyard bungalow in a Beijing hutong all her life.

This winter, however, the stove has disappeared from the 66-year-old's life, an electric radiator taking its place beside her bed, the product of a government-aided initiative to promote clean energy in the national capital.

With the Olympics to be staged in Beijing next August, the city is determined to eliminate the use of coal within the Third Ring Road that circles the city before the Games. The project to replace the stoves with electric radiators has been part of the effort.

When the city's four-month long heating season started on Thursday, coal-fired stoves, cited as a big source of pollution in the metropolis, have disappeared from some 20,000 local households like Zhao's bungalow in the inner city "hutong" -- traditional imperial-era alleyways that date back centuries.

"We used to boil water or bake bread on the stove," said Zhao, sounding sentimental to the disappearance of the coal furnace from her life.

The pensioner has long understood that an electrical heater would relieve her from that familiar choking smell as well as the black soot in her bungalow. But the family, which survives on the government's minimum living allowance, could not afford to switch to the more expensive electricity for winter heating, not even after a coal gas poisoning almost took her husband's life in 2003.

Only after 40 treatments sessions in a hospital hyperbaric oxygen chamber did he escape life-threatening danger.

At Zhao's small 20-square-meter house her family shares a courtyard with five other households in Xiyizi Hutong in Xicheng District.

The city currently has about 400-plus hutongs, mainly in the inner city's Xicheng and Dongcheng (meaning west town and east town, respectively) districts. The number is down from 6,000 in its prime during the Qing Dynasty (1644-1911). With the fast pace of today's real estate development, there are not many bungalows left in the city's hutongs.

The population density of Beijing's hutongs is about 49,000 people per square kilometer, nearly triple the city's average of 14,000 inhabitants per square km, and much higher than the 4,000 per km in New York.

In addition, Beijing's air quality monitoring office found that the emission of sulphur dioxide and carbon monoxide from the hutong areas have been higher than the city's average in winter, mainly because of the coal stoves. With the project to switch to clean energy for heating launched in 1999, the emission level of the two poisonous substances decreased by 42 percent and 44 percent, respectively, this year from 2001 levels.

Zhao accepted the switch to an electrical radiator when the government promised it would be no more expensive than coal. An extra incentive was the temperature-adjustable radiator was provided nearly free of charge.

In order to make electrical heating affordable, the municipal government allows those living in bungalows a discount of 0.3 yuan per kwh of electricity, compared with the market price of 0.48 yuan per kwh. It also compensates poor families with 0.2 yuan for every kwh of electricity used.

Zhao said the fee for electrical heat for the entire winter was usually around 2,400 yuan (US$323) per household. With the government's subsidy, however, she only needed to pay about 500 yuan, nearly the same price as that for coal.

According to the Beijing Bureau of Environmental Protection, the number of stoves has been reduced by 90 percent and 70 percent in Xicheng and Dongcheng districts, respectively. A total of 1,105 small coal-fired boilers for centralized heating have been converted to natural gas.

The efforts have helped reduce the sulphur dioxide emissions by 10 percent year-on-year, resulting in a level lower than the national standard of 0.15 milligrams per cubic meter, the bureau said.

In addition, the municipal government has set tighter restrictions on construction works and steel and chemical plants to ensure good air quality.