What does the car's internal circulation mean?

[McAshlyn]

The internal circulation of a car refers to the process where the air inside the vehicle is heated or cooled and then recirculated back into the cabin. Below is a related introduction about internal circulation: 1. Principle: Car air conditioning systems generally have an electric or manual switch for internal and external circulation. When external circulation is used, the air conditioning draws air from outside the car, while internal circulation reuses the air inside the vehicle. If the air conditioning internal/external circulation switch is a mechanical lever instead of a button, the lever can be placed in the middle position between internal and external circulation, allowing an appropriate amount of outdoor air to enter. This improves air quality while enhancing the air conditioning effect. 2. Advantages: Internal circulation primarily helps to promptly and effectively prevent external dust and harmful gases from entering the cabin, such as when driving through areas with smoke, dust, unpleasant odors, or in heavy traffic, blocking harmful exhaust emissions from vehicles ahead. Internal circulation can improve the cooling and heating efficiency of the air conditioning system and provides better insulation.

[DiBennett]

The interior recirculation is activated by pressing the button with the car icon on the AC panel, which stops the AC system from drawing air from outside and instead recirculates the air inside the car. After driving for ten years, I've found this feature most practical in traffic jams to avoid inhaling exhaust fumes from the car ahead, and also in quickly cooling down the car after it's been baking in the summer sun. However, don't keep it on all the time—prolonged lack of fresh air can cause dizziness. I usually switch back to exterior circulation after half an hour to get some fresh air. It's also useful in winter for defogging when paired with warm air, but remember to switch to exterior circulation when fogging is severe for faster dehumidification.

[SanLilliana]

Simply put, the interior air recirculation mode is like turning on the AC with the windows closed, similar to how we use air conditioning in a room without opening windows. I particularly like using it when driving through tunnels or near chemical plants on highways, as it effectively blocks unpleasant odors. However, you need to watch out for windshield fogging, especially when using recirculation on rainy days as the glass tends to frost up quickly—that's when you should switch modes. Additionally, it's best not to use it continuously for over an hour on long trips to avoid feeling stuffy; I usually switch to fresh air mode for a few minutes every three songs.

[SanHannah]

This feature is very easy to operate: just press the button on the AC panel with an arrow circulating inside the car. It's most noticeable in summer - after activation, the AC cooling efficiency skyrockets, making the cabin comfortable within just two minutes when it's 35°C outside. I also use it when encountering sprinkler trucks or hazy days in the city, as it essentially adds an air filter to the cabin. The only caution is not to keep it on for too long. Once I forgot to switch it off and used it continuously for two hours, and felt dizzy when getting out of the car - later I learned it was due to CO₂ buildup.

[Morales]

When the interior air recirculation is turned on, the air conditioning does not draw air from outside the vehicle, only recirculating the existing air inside. This feature is particularly useful during sandstorm weather. Last year during a self-drive trip in Xinjiang, it helped keep the air inside the car clean. However, it's important to note that the defogging effect may be reduced, especially during the humid 'Hui Nan Tian' season in southern China, so it's necessary to use it in combination with the defogging function. It's best to develop the habit of switching modes according to the situation. For example, five minutes before entering a service area on the highway, I switch to exterior air circulation to let fresh air in first.

[Maureen]

The button with the icon of air circulation inside the car represents this function. I've found several must-use scenarios: it can save about one-third of the time when quickly cooling down with AC after the car has been exposed to the sun in summer, it's very effective in preventing exhaust fumes during traffic jams, and it keeps out unpleasant odors when passing by garbage dumps or farmlands. However, the AC filter needs to be replaced regularly—I change mine every six months, otherwise, the circulated air can become dirtier. Here's a cool fact: using the recirculation mode when heating in winter significantly saves fuel, approximately 0.3 liters per 100 kilometers.