Recirculation Mode

It cools or heats the cabin faster because the system works on air that is already closer to the target temperature. It helps keep outside smells, dust and exhaust fumes out, for example in tunnels or heavy traffic. Some cars switch it automatically using an air-quality sensor that detects pollutants outside.

A flap at the air intake moves from the outside-air position to the cabin-air position, so the blower draws air from inside the car.

Leaving recirculation on for a long time raises humidity and carbon dioxide inside, which can fog the windows and make the driver tired. For demisting, use fresh air with the air conditioning on rather than recirculation.