Is it better to use internal or external air circulation when turning on the car's air conditioning?

[Preston]

Both internal and external air circulation can be used when turning on the car's air conditioning, as there are no strict requirements. A better practice is to alternate between internal and external air circulation. Internal circulation is mostly used during traffic jams, as it can isolate the outside air and prevent polluted air from entering the car. External circulation is mostly used during long drives, as it allows fresh air from outside to enter the car. Internal circulation means that the air blown by the blower only circulates inside the car. Since no external air is involved, it has the advantages of saving fuel and providing faster cooling or heating, but the disadvantage is that it is not conducive to refreshing the air inside the car. External circulation means that the blower draws air from outside the car and blows it into the car. The advantage is that it maintains the freshness of the air inside the car, but the cooling or heating speed is slower.