What does the car's internal and external circulation mean?

[McOlivia]

Internal and external circulation in a car refer to: Internal circulation closes the airflow passage between the inside and outside of the car. When the fan is turned on, there is no airflow circulation, and the air drawn in by the fan comes only from inside the car, forming an internal airflow cycle. External circulation uses the fan to draw air from outside the car into the interior, meaning the air passage between the outside and inside of the car is open. The air blown by the fan comes from outside the car, and even if the fan is not turned on, airflow is still drawn into the car while driving, replenishing fresh air inside. The symbols for internal and external circulation are: 1. The internal circulation symbol is a small car shape with a rotating arrow inside; 2. The external circulation symbol is an arrow passing from the front windshield into the car.

[DiRose]

When I first started driving, I wasn't quite clear about the air recirculation function either. I just knew I had to switch it when the AC felt stuffy. Simply put, the recirculation mode keeps the air inside the car circulating - the AC keeps blowing the same air mass. This helps retain warmth in winter or cool down faster in summer while saving fuel. The fresh air mode, on the other hand, draws in outside air. It keeps you cool with AC on, though less efficient in summer and consumes more gas. I often use recirculation in traffic jams to block exhaust fumes. On highways or rainy days, I switch to fresh air mode for better ventilation and faster defogging. Just remember not to use recirculation mode continuously - stale air can cause dizziness. The fresh air mode feels most refreshing when driving in open areas.

[CassidyRose]

As a seasoned car owner, I've found the air recirculation mode incredibly practical after years of driving. The interior circulation blocks external dust and noise while only processing cabin air, making AC cooling/heating remarkably fast. The fresh air mode draws outside air in, working wonders for defogging on rainy days – though you should be cautious about pollutants in urban areas with poor air quality. My habit is using recirculation for short trips to save fuel, then switching to fresh air on long drives to prevent motion sickness. The key is adapting to situations – like turning off recirculation briefly to exchange air when the cabin gets too warm in winter. Remember safety first: prolonged recirculation may cause oxygen depletion and driver fatigue, so it's best to switch to fresh air mode every half hour for ventilation.

[SanCharlotte]

The internal and external circulation are two modes of the car's air conditioning. Internal circulation uses the air inside the car, with no fresh air coming in unless you open the windows; external circulation draws in outside air to keep it fresh. You can switch between them with a button while driving, which is quite convenient. Use internal circulation in traffic jams to avoid exhaust fumes and cool down faster in summer; external circulation is great for air exchange on highways, especially useful after removing odors or smoking. With my automatic air conditioning, I often use the AUTO button, which switches between them automatically—very hassle-free. Don't forget to check the cabin air filter regularly; a dirty one can affect these functions and your health.