Should the car air conditioning use internal or external circulation in summer?

[VanJohnny]

Whether to use internal or external circulation for the car air conditioning in summer is not determined by the season but rather by a comprehensive assessment of the driving environment. Below are the relevant details: 1. The difference between internal and external circulation: The most obvious distinction between internal and external circulation in car air conditioning is the air intake location. Different intake positions result in different airflow movements. 2. Internal circulation explained: The air intake is inside the car, meaning outside air cannot enter, and inside air cannot exit. Prolonged use of internal circulation can lead to stale air, reduced oxygen levels, and symptoms like heat discomfort, fatigue, and anxiety, which can affect driving safety. 3. External circulation explained: The air intake is located below the front windshield wiper, at the junction of the windshield and the engine hood. Simply put, it draws outside air into the car. External circulation ensures air flow inside the car and is suitable when the outside air quality is good. 4. Tips for using internal and external circulation in car air conditioning: (1) If the car has been parked under the sun for a long time and the interior feels like a sauna, it is best to first turn on external circulation for ventilation and cooling after getting in. Opening the windows and sunroof can also speed up cooling. After 3-5 minutes, when the interior temperature stabilizes, close the windows, turn on the cooling function, and switch to internal circulation. (2) If the car is parked in a garage or a shaded area, it is recommended to first use internal circulation to maximize the cooling effect of the air conditioning and lower the interior temperature more quickly. (3) During traffic jams, use internal circulation to prevent external circulation from drawing exhaust fumes into the car. (4) Whether cooling in summer or heating in winter, periodically switch to external circulation to maintain air exchange between the car interior and the outside environment.

[EvangelineLynn]

In summer when driving with the AC on, I usually start with the recirculation mode to cool down quickly. When first getting in the car, the cabin feels like an oven—using recirculation lets the cold air circulate inside a few times, and the temperature drops instantly, making it much more comfortable. Once the cabin cools down, I switch to fresh air mode for ventilation. Otherwise, the air gets stuffy, accumulating humidity and odors, which can make you drowsy during long drives. Having driven for over a decade, I find this habit quite practical—recirculation saves energy and fuel, while fresh air keeps the air clean, especially on highways where ventilation also prevents window fogging. Just remember, if the outside air quality is poor (like on smoggy days), delay switching a bit. This simple and efficient routine ensures a comfortable drive every time.

[MacPresley]

I believe paying attention to in-car air quality is most crucial. In summer heat, I first use recirculation mode to let the AC cool the car quickly - it only takes a few minutes to bring down the temperature. Then I decisively switch to fresh air mode, because prolonged recirculation leads to CO₂ buildup and stuffy air, making me dizzy after long drives. Introducing external fresh air ensures smoother breathing and reduces fatigue, especially important for long-distance driving safety. I always remind myself not to be lazy - proper air circulation brings significant health benefits. If outside pollution is severe, I simply wait for cleaner conditions before switching modes. This approach achieves both rapid cooling and body care - killing two birds with one stone.

[GideonFitz]

When turning on the AC, I prefer starting with the recirculation mode first—it instantly feels refreshingly cool and super comfortable. Once the cabin temperature stabilizes, I switch to fresh air mode to ventilate, preventing stuffiness. The influx of fresh air keeps me alert and makes driving more energetic. This straightforward and reliable method eliminates any hesitation—just get it done. That's how I roll in summer, hassle-free and efficient.