Which air circulation mode to use for defogging inside the car?
3 Answers
Turn on the external air circulation mode and activate the warm air when defogging inside the car. This introduces dry air from outside, which then gets heated by the warm air system to produce dry, high-temperature air that can effectively eliminate interior fogging. During winter, the outside air is typically dry, while the interior accumulates significant moisture from human respiration. When this moist air contacts the cold windshield, it forms condensation. A special case occurs in southern winters where humidity levels are high. In such conditions, turning on the air conditioning proves more effective for defogging, as the airflow passing through the AC evaporator causes substantial water vapor to condense and liquefy, resulting in relatively drier air.
I remember a few years ago when I drove my family on a winter trip, the car windows fogged up, and the entire windshield became blurry, scaring me so much that I almost couldn't brake in time. Later, a friend taught me that in such situations, I should directly turn on the external circulation button to let fresh air from outside come in. This way, the humidity inside the car can be expelled, and the fog will dissipate quickly. Fogging mainly occurs because the moisture from our breath condenses on the cold windows. Turning on external circulation introduces drier outside air, which solves the problem. To prevent fogging in daily use, it's best to keep the inside of the windows clean, avoiding fingerprints or stains that could worsen moisture accumulation. Safety comes first when driving. If fogging occurs, don’t hesitate—immediately turn on external circulation and avoid using internal circulation, as it will only make things worse by recirculating the moisture inside the car.
Fogging inside the car is a real safety hazard, as it can impair visibility and lead to accidents in the blink of an eye. As a veteran long-distance driver, my top recommendation is to first activate the external circulation mode. This allows drier outside air to replace the humid air inside. Increasing the fan speed enhances the effect. For severe fogging, you can also turn on the heater or air conditioning dehumidification function simultaneously, but the core solution still relies on external circulation. Remember not to use internal circulation—it merely recirculates the moist air inside, worsening humidity buildup. Regularly checking if the car's air filter is clogged can also help improve ventilation and prevent fogging. Safety always comes first; develop the habit of calmly handling fogging situations without panic.
