Should You Use Internal or External Air Circulation When Turning on the AC?

[AnthonyMarie]

The best practice when turning on the AC is to alternate between internal and external air circulation. Although using internal circulation in summer is more fuel-efficient and provides the best cooling effect, prolonged use can lead to "air conditioning sickness," especially when idling in the car with the AC on, which may cause carbon monoxide poisoning. Below is an introduction to the two air circulation modes: 1. Internal circulation: The air blown by the blower circulates only inside the car. Since no external air is involved, internal circulation is fuel-efficient and cools (or heats) quickly, but the downside is that it hinders air renewal inside the car. 2. External circulation: The blower draws air from outside the car and blows it inside. The advantage is that external circulation maintains fresh air inside the car, but it consumes more fuel and cools (or heats) more slowly.