Why is the air volume greater in car's internal circulation than external circulation?

[Zane]

Car's internal circulation has greater air volume than external circulation because internal circulation not only needs to cool but also dehumidify, hence requiring more airflow. Below are detailed explanations about car's internal and external circulation: 1. Differences: Generally, external circulation is used when outside air quality is good, while internal circulation is used when outside air quality is poor. Additionally, external circulation should be used on highways, and internal circulation should not be used for prolonged driving. 2. Precautions: Driving on highways often involves long-distance travel, requiring the use of external circulation due to extended driving time. If internal circulation is used, because the vehicle is sealed and air cannot exchange with the outside, oxygen inside the car is consumed by breathing, leading to decreased oxygen levels and making the driver more prone to fatigue.