Audi Q5   Controls   Heating and cooling  3-zone deluxe automatic air conditioner
The air recirculation setting prevents fumes etc. from entering the interior.
Switching on the air recirculation mode
Press the button WARNING!.
Switching off the air recirculation mode
Press the button again, or
Press the AUTO button, or
Press the button.
In this setting, the air is drawn from the interior of the vehicle, filtered and continuously recirculated. We recommend using the air recirculation mode in the following circumstances:
When driving through a tunnel or in queues of traffic, to prevent fumes entering the interior of the vehicle.
WARNING!
For reasons of safety you should not leave the air recirculation switched on for too long. This mode prevents fresh air from entering the vehicle, so the windows can mist over if the air cooling is switched off. Bad visibility can cause an accident.