Is it better to use the internal or external circulation when turning on the air conditioning in a sedan?

[DeLuke]

When turning on the air conditioning in a car, it is best to alternate between internal and external circulation. Here is some relevant information: 1. Internal circulation means that the air blown by the blower circulates inside the car. Since no external air is involved, it has advantages such as fuel efficiency and faster cooling (or heating), but the disadvantage is that it is not conducive to updating the air inside the car. 2. External circulation means that the blower draws fresh air from outside the car into the interior. The advantage is that it ensures air quality inside the car, but cooling (or heating) is slightly slower and it consumes more fuel. 3. In summer, when turning on the air conditioning, you should first open the windows to ventilate and allow the car to dissipate heat, lowering the interior temperature before turning on the air conditioning. Start with internal circulation, and once the interior temperature drops to a suitable level, switch to external circulation to maintain fresh air inside the car. 4. In winter, it is not advisable to use internal circulation because the outside air is dry and cold, while the interior tends to be more humid, leading to condensation. In this case, external circulation should be used to introduce the dry, cold air from outside into the car.

[DeDakota]

Using recirculation or fresh air mode for cooling depends on the situation. When I drive, I mainly consider two factors: cooling speed and air quality. Right after turning on the AC when the car is extremely hot, I use recirculation mode for the fastest cooling effect, as it only processes the air inside the cabin, making cooling more direct and efficient. Once the temperature drops to a comfortable range, I switch to fresh air mode to maintain airflow and prevent oxygen deprivation, especially during long drives when window fogging can impair visibility. In heavy traffic or when passing through industrial areas with poor air quality, I switch back to recirculation to prevent exhaust fumes from entering the cabin. My recommendation is to use fresh air mode 80% of the time, reserving recirculation for the remaining 20% to handle extreme conditions.

[VanTaylor]

Having driven for over a decade, I'm most qualified to answer this. The optimal way to use AC is alternating between recirculation and fresh air modes. Upon entering the car, use recirculation for five minutes to cool down quickly, then switch to fresh air when the thermometer shows around 25°C. Recirculation acts like a mask against foul odors, especially crucial during urban rush hour traffic with heavy exhaust fumes. However, prolonged recirculation causes CO₂ buildup leading to drowsiness - my friend nearly had an accident on the highway because of this. Additionally, switch to fresh air two minutes before parking to dry the AC ducts and prevent mold growth.

[VanHenry]

Here's a practical tip for using AC in summer: prioritize recirculation mode for short trips, but always switch to fresh air mode on long drives. Last week during the school run rush hour, I kept it on recirculation the whole way - blocked exhaust fumes and saved fuel. But on our last road trip, I forgot to switch to fresh air and the whole family got dizzy and nauseous. Now I keep a reminder sticky note on the dashboard: 'Switch to fresh air every 30 minutes'. If outside temperature is cooler than inside, immediately switch to fresh air mode - it works like a natural cooler.

[DiSebastian]

Air conditioning settings are crucial when traveling with kids. For cooling, I adhere to the three-minute rule: circulate air rapidly for the first three minutes to cool down quickly, then switch to fresh air mode to maintain air quality. Kids in the back seat are most vulnerable to stuffiness, so I always clean the fresh air intake vents with disinfectant wipes. Recently, I discovered a great trick: turning on the seat ventilation function in fresh air mode allows cool air to rise from the footwell, creating exceptional comfort. On rainy days when using cooling, remember to activate the rearview mirror heating function - combining this with fresh air mode prevents fogging effectively.