Should the car air conditioning use internal or external circulation when cooling?

[Kira]

When cooling with the car air conditioning, you should first turn on the external circulation, then switch to internal circulation. After getting in the car, start with external circulation to ventilate and dissipate heat, while also opening the windows and sunroof to speed up heat dissipation. After 3-5 minutes when the interior temperature has stabilized, close all windows, turn on the cooling, and switch the air conditioning to internal circulation. Definition of internal circulation: Internal circulation is a state of the car's air conditioning system. In this state, the air exchange channels between the inside and outside of the car are closed. When the fan is off, the air inside does not circulate; when the fan is on, the air drawn in comes only from inside the car, creating an internal air flow cycle. Function of internal circulation: The main function of internal circulation is to block polluted air, prevent outside air from entering the car, and maintain clean air inside the vehicle. It can quickly cool the car, but even with internal circulation on, about 20% of the air still exchanges with the outside, meaning it is not completely sealed.