一坐高铁就犯困”，铁路专家回应网传“高铁二氧化碳超标

Core Viewpoint - The reported CO2 concentration levels in high-speed train carriages have been clarified by experts, indicating that the standards for rail vehicles differ from those for civilian buildings, and the levels observed do not pose health risks to passengers [1][2]. Group 1: CO2 Concentration Standards - The standard limit for CO2 concentration in passenger trains in China is set at a maximum of 2500 ppm according to TB/T 3493-2017, while European standards allow up to 5000 ppm [1]. - The viral claims regarding CO2 levels were based on GB 50736-2012, which applies to civilian buildings and is not relevant to passenger trains [1]. Group 2: Air Quality Management in Trains - High-speed trains are designed with a fully sealed car body, relying on air conditioning systems for ventilation, providing over 15 m³/h of fresh air per person, with air exchange rates of 6 to 12 times per hour [1]. - During normal operation outside tunnels, CO2 levels typically do not exceed 1500 ppm, but can temporarily rise above 2000 ppm when passing through tunnels due to pressure protection measures [2]. Group 3: Public Reaction and Observations - A video showing CO2 levels rising in a second-class carriage sparked public discussion, with initial readings around 880 ppm increasing as passengers boarded, leading to a perception that high-speed travel induces drowsiness [2].