High-speed train experts: The standard limit value of indoor carbon dioxide concentration for passenger trains in China is 2500ppm, and concentrations within this limit have no impact on health.

On January 23, in response to the online rumor that "the carbon dioxide concentration in the high-speed train carriages exceeded the standard limit of 1000ppm", Tao Guidong, an expert from CRRC Qingdao Sifang Co., Ltd., explained that the EMU trains have fully airtight carriages, and the ventilation is entirely provided by the air conditioning system. The average fresh air volume per person exceeds 15m/h, with ventilation occurring 6 to 12 times per hour. In addition, the EMU trains are equipped with a pressure protection system. During operation in non-tunnel sections, continuous ventilation can be achieved, and the carbon dioxide concentration generally does not exceed 1500ppm. When passing through a continuous tunnel group, in order to reduce passengers' discomfort caused by fluctuations in external air pressure, the train will take pressure protection measures by closing off the connection with the outside air. At this time, the exchange of indoor and outdoor air cannot be achieved, and the carbon dioxide concentration in the carriages may temporarily increase, but it will not have any impact on the passengers' health.