How to Distinguish Between Car's Internal and External Air Circulation?
3 Answers
Car's internal and external air circulation are distinguished as follows: 1. External circulation refers to drawing air from outside the car, directing it to the air conditioning system for heating or cooling, and then blowing it out from the vents. External circulation essentially supplements fresh air to improve the air quality inside the car. It is used in situations like defrosting in winter or defogging in summer because the air drawn from outside contains higher oxygen levels and is drier, making defrosting or defogging more effective. 2. Internal circulation, on the other hand, draws air from inside the car, creating a cycle of airflow within the vehicle. The main function of internal circulation is to promptly and effectively prevent external dust and harmful gases from entering the car. It helps in warming up the car faster in winter and cooling it down quicker when the air conditioning is on in summer. It can also be used during smoggy days. Internal circulation means the air inside the car is recirculated, helping to maintain the car's interior temperature more effectively.
When driving, I distinguish between recirculation and fresh air modes mainly by the button icons: the recirculation button usually shows a car icon with an arrow circulating inside, meaning air only recirculates within the cabin; the fresh air mode has an arrow pointing from outside into the car, indicating outside air is drawn in. When using AC, I select recirculation if I smell external pollution or want rapid cooling; on highways or when fogging occurs, I switch to fresh air mode for ventilation and anti-fogging. Additionally, manual testing is intuitive: with windows open, airflow changes when switching modes—fresh air mode delivers stronger, cooler airflow while recirculation feels gentler with fewer external odors. Long-term incorrect usage affects AC efficiency, so I regularly check button positions to ensure proper selection.
As someone who frequently travels with kids, I made sure to understand the circulation system when learning to drive: the recirculation mode keeps air enclosed within the car, indicated by a button with a car surrounded icon; the fresh air mode draws in external air, shown by an arrow pointing into the car. A simple way to remember is to try it while driving—switching to recirculation instantly blocks external pollen or smoke smells; turning on fresh air reduces window fogging. Especially in humid weather, I always use fresh air to prevent windshield fogging. The AC settings also have an auto mode that switches intelligently, but I prefer manually checking the button position for peace of mind.
