What is the difference between the internal circulation and external circulation in a car?

[LaRyder]

The differences between the internal circulation and external circulation in a car are: 1. Different meanings: Internal circulation refers to the air inside the car being heated or cooled before being recirculated back into the car; External circulation refers to drawing air from outside the car, heating or cooling it, and then sending it into the car, which means gas exchange between the inside and outside of the car. 2. Different uses: Internal circulation is used in urban roads with heavy traffic congestion; External circulation is used during high-speed driving when it is inconvenient to open the windows for ventilation. The external circulation mode uses a 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 car.

[LeAaliyah]

After driving a car for so many years, I've realized there's quite an art to using the recirculation and fresh air modes. The recirculation mode means the AC system only circulates the air inside the car, keeping out external dust, pollen or exhaust fumes - especially useful in areas with poor air quality, like during traffic jams or when passing construction sites. I've noticed it cools the car faster too, saving fuel and money. But using it too long makes the air stale and can cause dizziness, so I usually switch back to fresh air mode after 20-30 minutes for ventilation. The fresh air mode brings in outside air and is particularly effective at clearing fogged-up windows during rainy days - much clearer visibility, and safety comes first. My usual practice is to alternate between the two modes, never sticking to recirculation for too long as it affects health. Remember to pay extra attention to air circulation when there are more passengers to ensure comfortable breathing.

[LawsonMarie]

In my daily driving, I've experienced the difference between the recirculation and fresh air modes. The recirculation mode significantly reduces AC energy consumption as the vehicle doesn't need to process outside air, resulting in higher cooling efficiency. It's particularly effective for quick cooling and fuel savings during hot summer days. However, prolonged use leads to oxygen depletion inside the cabin, creating a stuffy and uncomfortable feeling. The fresh air mode introduces outside air, ideal for clean environments like rural roads where it feels as refreshing as opening windows. A key distinction is that fresh air mode also prevents window fogging and works well for dehumidification during rainy days. I recommend switching between modes based on real-time weather and air quality - use recirculation when outside pollution is high to protect your breathing, and fresh air mode in clean environments to maintain ventilation. Developing this habit enhances driving comfort and benefits your health.

[LaNathan]

As an ordinary person who drives frequently, I often use two circulation modes. The recirculation mode cycles the air inside the car repeatedly, filtering out external smoke, dust, or odors, which is suitable for hazy or heavy exhaust conditions. However, prolonged use can make the air inside the car stale and cause fatigue. The fresh air mode draws in outside air, which helps quickly defog windows and ensures safety during rainy days. I typically use recirculation for short trips and switch to fresh air mode for ventilation on long journeys. Alternating between these two modes creates a more comfortable and safer in-car environment.