What is the difference between the internal and external circulation of car air conditioning?
3 Answers
Internal circulation means not allowing outside air to enter the car. Due to the limited space inside the car, if the windows are closed and internal circulation is used for a long time, the car will quickly fill with moisture from human respiration, and the oxygen level will also decrease. External circulation, simply put, is to expel the air inside the car and draw in fresh air from outside. Here is an introduction to the selection of car air conditioning modes: Summer: Use internal circulation more often when the air conditioning is on in summer. Winter: Use external circulation more often when the heater is on in winter. When air quality is poor: Use internal circulation when air quality is poor, otherwise use external circulation.
I drive a small SUV for my daily commute and find that using the recirculation mode is crucial during city traffic jams. It maintains stronger cooling effects, prevents outside exhaust fumes from entering, and allows for quicker cooling in summer and faster heating in winter. However, prolonged use can make the air feel stuffy. On the other hand, the fresh air mode draws in outside air, which is especially comfortable after traffic clears or on sunny days when windows are open for ventilation. It helps circulate air inside the car and prevents window fogging—for example, I rely on it to defog windows on rainy days. The key difference is that recirculation mode saves fuel and offers better sealing, while fresh air mode improves ventilation but may draw in dirty air, increasing the AC load. For long-term use, I recommend using recirculation mode more during rush hour to reduce pollutant intake and switching to fresh air mode on highways to improve air quality and stay alert.
I always pay attention to fuel consumption and environmental issues. As a hybrid car owner, I've studied the impact of air conditioning modes on energy consumption. In recirculation mode, the AC cools or heats more efficiently with faster temperature adjustment and lower compressor load, theoretically saving more electricity—ideal for quick temperature regulation. However, fresh air mode introduces outside air, reducing CO2 concentration inside the cabin, which theoretically improves engine efficiency and reduces driver fatigue, such as preventing drowsiness during long trips by breathing fresh air. The key difference lies in one mode recycling internal air for energy savings but potentially causing stuffiness, while the other draws in external air for better air quality but may increase intake burden, especially in polluted urban areas. My approach is to use recirculation in congested areas to avoid external pollution, then switch to fresh air mode in suburbs or on highways to balance energy savings and air quality.
