The “recirculation of air”, or “air recirculation”, button is an important part of the air conditioning in your car, but its use may seem mysterious to some. So, what exactly is it for and when should you activate it?
The air recirculation button allows you to close access to outside air and recycle the air already inside the car. This is a function that has several uses. First, it allows the cabin to cool or heat more quickly. In fact, the indoor air, already partially conditioned, consumes less energy to reach the desired temperature. Second, it is useful for preventing the intrusion of unpleasant odors or external pollutants, such as exhaust fumes on a congested highway.
However, it is important not to use the recycle function continuously. Recirculated air can become depleted of oxygen and loaded with carbon dioxide, which can cause drowsiness and headaches in car occupants. Also, humid air generated by breathing can cause windows to fog up, reducing visibility.
It is therefore recommended to use the air recirculation button mainly for rapid heating or cooling of the passenger compartment, or to avoid occasional external pollutants. But it is then necessary to return to outside air intake mode to renew the air in the car.
There are situations where you should never activate air recirculation, particularly when there is frost or mist on the windows. In fact, air recycling does not effectively defog the windows, since it maintains humidity inside the vehicle. To defog, it is best to use heating with outside air, which is generally drier.