A maintenance worker installs the filter of the air-conditioning evaporator of a train at Zhengzhou high-speed railway maintenance station in Zhengzhou, central China's Henan Province, Feb. 12, 2020. Maintenance workers did the cleaning of the air-conditioning system on the high-speed trains at Zhengzhou high-speed railway maintenance station Wednesday to guarantee the clean air flow on the carriages during the fight against the novel coronavirus epidemic. As the number of people back to work has shown an upward trend, Zhengzhou high-speed railway system has increased the frequency of cleaning and disinfection of the air-conditioning system and other facilities. (Xinhua/Li An)