Should You Use Internal or External Air Circulation When Running the Car AC in Summer?
2 Answers
Choosing between internal and external air circulation when running the car AC depends on specific circumstances. Here are the key considerations: External Circulation Mode: This mode uses the fan to draw outside air into the car, meaning the air passage between the exterior and interior remains open. The air blown by the fan comes from outside, and even with the fan off, airflow is still drawn into the car while driving, replenishing fresh air inside. Sometimes, you may feel airflow even when the fan is off—this occurs because external circulation is enabled. In urban traffic jams, the car may fill with exhaust fumes due to external circulation drawing in surrounding vehicle emissions. Internal Circulation Mode: This mode closes the airflow passage between the inside and outside of the car. Without the fan, there is no airflow circulation, and when the fan is on, the airflow is drawn solely from inside the car, creating an internal air loop. Internal circulation primarily blocks external dust and harmful gases from entering, such as when driving through smoke, dust, areas with strong odors, or dense traffic, preventing harmful exhaust from preceding vehicles. Another benefit is maintaining cabin temperature.
In summer, I prioritize using the air recirculation mode when turning on the AC because it cools down the car much faster. Especially when first getting into a scorching hot car, recirculation prevents outside heat from entering and only cycles the cooled air inside, making it comfortable within minutes. After about 30 minutes, I switch to fresh air mode to ventilate the cabin and avoid stuffiness, which can cause drowsiness. I remember once forgetting to switch during a long drive, and my wife complained of dizziness. In smoggy or heavy traffic conditions, recirculation reduces pollutant intake. While fresh air mode provides better ventilation, it’s less efficient in summer unless outside air is clean. Overall, I mainly use recirculation with brief fresh air intervals to balance air quality. Automatic climate control makes this easier, but manual adjustment isn’t troublesome either. Developing this habit makes summer driving more comfortable and worry-free.
