Beijing released a revised standard for cleaner coal and related coal products on Thursday, the latest move to reduce air pollution especially in rural areas.

The sulfur content of coal products will be less than 0.4 percent from the current 0.5 percent, according to the standard released by Beijing Environmental Protection Bureau.

The standard was the strictest one among similar regional standards for coal use, said Wang Zhongmin, an engineer in Beijing's coal quality supervision station.

The government will promote the use of the high-quality coal with low sulfur, and the standard is expected to cover the capital before 2017, said Liu Wei, an officer for the atmosphere department under the bureau.

According to the bureau, coal was still the major source of air pollution in Beijing and about 30 percent of sulfur dioxide emission was from the use of coal by residents. Suppliers of low-sulfur coal will get a 200 yuan ($32.68) subsidy per metric ton from the government.

The revived standard was part of a clean-air action plan unveiled last week in Beijing. According to the plan, Beijing pledged to reduce PM2.5 density by a minimum of 25 percent by 2017.