The Beijing Subway announced Saturday that all trains running on the Batong Line, which extends from the eastern terminus of Sihui Dong to the residential areas of Tongzhou District, would be air conditioned. 

There are currently 24 trains running on the Batong line. So far 11 trains are air-conditioned and the remaining 13 will be completed this summer.

Since the Batong section began operating in 2003, there have been frequent complaints about the conditions inside the carriages, especially during summer. 

2005/03/07
Source: Beijing Portal