High-speed train feeling sleepy as soon as you sit down? Netizens claimed that the carbon dioxide concentration in the carriage exceeded the standard during actual tests, and 12306 responded to the issue of air cleanliness.

Recently, a netizen posted a video claiming that the carbon dioxide concentration in a high-speed train carriage exceeded the recommended 1000ppm limit in the national "Indoor Air Quality Standard". The customer service of 12306 responded that the staff would clean the carriage, but there might not be a specific cleaning procedure for the air.