Which is the external circulation mode for cars, A or M?

[OGavin]

In cars, 'A' stands for automatic control of the internal and external air circulation, while 'M' represents the external circulation mode. When the 'A' button is activated, the air conditioning system automatically determines whether to use internal or external circulation based on the outside air quality. When the 'M' button is turned on, the car is in internal circulation mode if the light is on, and in external circulation mode if the light is off. The functions of internal and external circulation in cars are different: Function of external circulation: External circulation primarily serves the purpose of ventilation. When the air inside the car becomes stale, the external circulation should be activated to refresh the cabin air. Function of internal circulation: When internal circulation is engaged, the air inside the car does not exchange with the outside, and the airflow circulates within a closed environment.