Should You Use Internal or External Air Circulation in a Car During Winter?
3 Answers
In winter, it is recommended to first use the internal air circulation in your car and switch to external circulation once the interior has warmed up. The internal circulation mode closes the airflow passage between the inside and outside of the car, creating an internal airflow cycle. This effectively prevents external dust and harmful gases from entering the car while maintaining the interior temperature. The external circulation mode uses a fan to draw air from outside into the car. Even if the fan is off, airflow will still enter the car while driving, replenishing fresh air. The differences between external and internal circulation in a car are: 1. Different air circulation methods: External circulation draws air from outside the car, which is then cooled or heated by the air conditioning system before being blown out through the vents; internal circulation draws air from inside the car. 2. Different functions: External circulation brings fresh air into the car to maintain air quality, while internal circulation effectively blocks external dust and harmful gases, enhancing the cooling and heating efficiency of the air conditioning system.
I've been driving for ten years, and the most annoying thing in winter is the fogged-up windows. Last week during the snow, I made a mistake: I kept the recirculation mode on for too long, and suddenly the windshield became foggy—I almost hit the guardrail. Later, I figured out that after starting the car, I should first turn on the external air circulation and blast the windshield until the fog clears, then switch to recirculation to keep warm. If you feel drowsy while driving on the highway with the heater on, it’s probably due to lack of oxygen from prolonged recirculation—switch to external air immediately to ventilate. Remember, don’t just wipe the fog with a cloth; using external air plus cold air blowing on the glass is the fastest way to clear it. If you notice water droplets on the windows even with recirculation on, it means there’s a moisture source inside the car—check if snow was brought in on the floor mats. Friends in the north, especially, should pay attention: alternating between internal and external air circulation is a life-saving trick.
Last time I heard the auto repair shop owner complaining, three out of ten towed cars were due to winter confusion. Using the recirculation mode does save fuel and keep warm, but after half an hour, the carbon dioxide concentration in the car exceeds the standard, leading to brain hypoxia and slower reactions, which is too dangerous for highway driving. My own operating mantra is: use recirculation mode in city traffic to prevent exhaust fumes, and switch to fresh air mode on the highway for ventilation. Don’t panic on smoggy days either; new cars now have air detection functions that automatically switch between recirculation and fresh air modes, with prompts from the car system. On long trips, I deliberately press the fresh air button every half hour to defog and stay alert. Remember last year’s news about a family who almost suffocated sleeping in the car with recirculation on—this bloody lesson must not be forgotten.
