Is it better to use the internal or external air circulation on the highway?
2 Answers
It is better to use the external air circulation on the highway. The external circulation of the car's air conditioning can keep the air inside the car relatively fresh. When driving on the highway for a long time, using the internal circulation for an extended period can make the air inside the car become stale, increasing the concentration of carbon dioxide, which can cause the driver to feel fatigued and tired, seriously affecting driving safety. The external circulation can expel poor-quality air from the car and also be used to refresh the air inside the car. Below are the working principle and method for turning on the external circulation: Working principle of external circulation: The external circulation mode uses a fan to draw air from outside the car into the interior, meaning the air passage between the outside and inside of the car is open. The air blown by the fan comes from outside the car, and even if the fan is not turned on, airflow is still drawn into the car while driving, replenishing fresh air inside the car. Method to turn on external circulation: When the indicator light for the internal/external circulation button is off, it means the external circulation is turned on, replenishing fresh air.
Choosing between recirculation or fresh air mode on highways depends on specific scenarios. My experience is that I usually start with recirculation mode, especially when outside air quality is poor or dusty—it saves fuel since highway speeds make open windows noisy and unsafe. After some time in recirculation, if the cabin feels stuffy, I switch to fresh air mode for a few minutes to refresh, reducing drowsiness. In winter or rain, fresh air mode prevents faster window fogging, improving safety. Avoid staying in one mode too long—excess CO₂ buildup can cause fatigue and slower reactions. I typically alternate every 30 minutes to balance efficiency and comfort.
