Audi Q5   Controls   Heating and cooling  3-zone deluxe automatic air conditioner - basic settings
If the outside air is polluted, an air purity sensor in the vehicle will automatically switch on the air recirculation.
If the air purity sensor in the air conditioner system detects a certain concentration of fumes in the outside air, the control unit will either pass the incoming air through the pollution filter or automatically switch on the air recirculation. If there is a high concentration of pollution in the outside air, the air conditioner automatically switches to air recirculation and cuts off the supply of air from the outside. As soon as the level of pollution decreases, air is fed into the vehicle from the outside again.
If the windows mist up when the automatic air recirculation is on, press the button immediately.
The automatic air recirculation can switch itself off in certain conditions. If the outside temperature is less than about +10 °C, the automatic air recirculation will only operate for 30 seconds.