Internal and external circulation sign?

When the fan in the car is turned on, it can be used in external circulation and internal circulation, which can be realized by changing the switch. The identification of automobile external circulation and internal circulation is very simple and clear. The purpose of external circulation is to replenish fresh air, which is blown from outside to inside the car. The icon is a convertible with an air arrow pointing inward. Internal circulation is to circulate the air in the car when it is closed. This icon is a circular arrow in a closed car.