What is the difference between internal and external air circulation?
3 Answers
The differences between internal and external air circulation: 1. Different principles: Internal circulation keeps the air inside the car flowing in a closed environment; External circulation brings outside air into the vehicle. 2. Different air intake locations: Internal circulation draws air from inside the cabin, preventing outside air from entering; External circulation's air intake is located below the front windshield wiper, pulling outside air into the car. 3. Different effects: Prolonged use of internal circulation can make the air stale, reduce oxygen levels, cause discomfort like heat and fatigue, and affect driving safety; External circulation maintains air flow between inside and outside the car, preventing excessive carbon dioxide concentration.
Having driven for over a decade, the button I most often mention to beginners is the one with a car icon and an arrow on the AC panel. The recirculation mode is like sitting indoors with windows closed while using a fan—it only circulates the existing air inside the car. Turning it on immediately after getting into a sun-scorched car in summer speeds up cooling dramatically; turning it off during winter defogging can also save some fuel. The downside is that it can get stuffy with more passengers, and high CO2 concentrations may cause drowsiness. The fresh air mode is like opening windows for ventilation, constantly drawing in outside air. It feels especially comfortable on highways, and you might even catch the scent of grass on forest roads after rain. But remember to turn it off in traffic jams or near chemical plants—otherwise, exhaust fumes and unpleasant odors will flood in. My usual practice is to prioritize recirculation in the city and switch to fresh air mode on highways for ventilation, ensuring both comfort and extended AC lifespan.
As a dad of two, the worst thing about taking kids out is poor air quality inside the car. Using recirculation mode is like putting a mask on the car - pollen and smog from outside can't get in, which is great for kids with allergies. But you need to switch to fresh air mode for a few minutes every half hour, otherwise the kids will complain about feeling stuffy. Fresh air mode is like opening up the airways - especially nice when driving past parks in the early morning, as natural breeze feels much better than AC. However, I immediately switch back to recirculation when passing construction sites with lots of dust or when the car ahead is spewing black smoke. Here's a pro tip: use recirculation mode when first turning on the AC to cool down faster, then switch to fresh air once the temperature stabilizes to maintain airflow - it saves energy and keeps the air healthy.
