Basically, air inlet ensures that there is always some way for the fresh air to come into ventilated building/room. When the fan is working in a closed room/building it sucks out the air from it generating pressure. Air inlet is equipped with returnable flap which opens each time the fan is working. This happens because of the pressure difference between building and free space. When the fan stops, flap returns to its normal position (closed).
Product is also equipped with protection metal grid and additional panel for complete closing (e.g in winter conditions).
Shape of the inlet was designed to let the fresh air be sucked from the bottom, so that no water drops or snow could get inside. In practise inlet should be mounted in north or east side of the building, far away from any sources of impure air (e.g. rubbish dumps).
Air inlet is made of durable black plastic material.