Is the BMW 3 Series A for internal circulation or M?

[Hillary]

BMW's internal circulation A and M are two modes of the AUC (Automatic Air Recirculation Control) system in the vehicle. A stands for automatic internal and external circulation, which automatically determines whether internal or external circulation is needed based on the air quality inside the car. M stands for internal circulation. The functions of external and internal circulation are as follows: Function of external circulation: External circulation primarily serves the purpose of ventilation, so it should be activated when the air inside the car becomes stale. During high-speed driving, if the car is sealed and only internal circulation is used, it can easily lead to insufficient oxygen inside the vehicle, which may cause driver fatigue, lack of concentration, and pose potential hazards. Function 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 airflow inside the car does not circulate. When the fan is on, the air drawn in comes only from inside the car, creating an internal airflow circulation within the vehicle.