Choosing Between Internal and External Air Circulation for Car Air Conditioning in Winter
3 Answers
In winter, use internal circulation when turning on the heater. After starting the car, wait approximately 8-15 minutes for the water temperature to reach normal levels, then you can turn on the heater and switch the air conditioning to internal circulation mode. Difference between internal and external circulation: Internal circulation works by closing the airflow channels between the inside and outside of the vehicle. When the air conditioning is on, only the air inside the car circulates. Without the fan running, there is no air movement inside the cabin. External circulation operates by using the fan to exchange air between the inside and outside of the vehicle, bringing fresh air in from outside and expelling stale air from inside. Even without the fan running, the vehicle can still allow airflow to refresh the cabin air. Application scenarios for internal and external circulation: When driving on highways for extended periods, the air inside the vehicle can become stale, and opening windows may create excessive wind noise. In such cases, switching to external circulation can refresh the cabin air while filtering out poor-quality outside air. When driving in urban areas during rain, snow, or when outside air quality is poor, closing the windows and using the internal circulation mode of the car's air conditioning is a good choice. This blocks out poor-quality outside air, prevents breathing discomfort, helps maintain cool temperatures in summer, and keeps the cabin warm in winter.
As a driver who frequently drives in winter, I find that turning on the air recirculation mode helps the car warm up faster, as recycling the existing warm air is more efficient than heating cold air from outside. Using the fresh air mode introduces cold air, which can cause heat loss and slow down the warming process. However, don’t keep the recirculation mode on for too long—prolonged use can lead to stale air, CO₂ buildup (making you drowsy), and increased fogging. My suggestion is to use recirculation for the first 3-5 minutes to warm up the cabin, then switch to fresh air mode once the temperature is comfortable. This maintains airflow, prevents fogging, and is ideal for long drives—saving fuel and ensuring safety. Also, remember to use the defrost function for a smoother driving experience.
Having driven in the north for many years, I pay special attention to the health impact of car air conditioning in winter. I start with the recirculation mode to warm up the car quickly, otherwise it's freezing. But don't use it for too long, as poor air circulation can breed bacteria or worsen cabin pollution, especially when traveling with children. Switching to fresh air mode introduces outside air, reducing humidity differences to prevent fogging and ensuring clear visibility for safety. The ideal approach is to switch to fresh air mode after the car warms up, periodically opening windows for ventilation to ensure a comfortable and pleasant journey—never overlook the importance of air quality.
