What circulation mode should be used when turning on the car's air conditioning?

[ClaireLee]

When using the car's air conditioning for cooling, the internal circulation mode should be activated. 1. Internal circulation: This mode means the air conditioning system draws air from inside the vehicle, cools it through the compressor, and then recirculates it. The advantage of this circulation type is that it allows for rapid cooling or heating of the car interior. However, the drawback is that prolonged use of internal circulation may lead to decreased oxygen levels and increased carbon dioxide concentration inside the vehicle. 2. External circulation: This mode introduces fresh air from outside to improve air quality inside the car. It's typically used during winter defrosting or summer defogging operations, as outside air contains higher oxygen levels and is drier, making it more effective for these purposes.