Should the car use internal or external air circulation when running the AC in summer?

[SanBeau]

For regular cooling, first use internal circulation and then switch to external circulation. Here is some extended information about internal and external circulation: Introduction: External circulation draws air from outside the vehicle, filters it through the AC filter, and delivers it into the cabin via the blower. Internal circulation closes the air intake flap to block outside air. Whether using internal or external circulation, exhaust air inside the vehicle will be expelled through the vents, so there's no need to worry about oxygen levels even when using internal circulation. Application scenarios: Without fresh air intake, the cabin air can become stale and oxygen levels may drop. In this case, turn on external circulation to allow fresh outside air to enter the cabin for quick air exchange. When outside air quality is poor, promptly switch to internal circulation to prevent harmful gases from entering the cabin.