What are the methods to deal with fogging on the windshield?

[VonNova]

Press the defogging button, turn on the air conditioning cooling (A/C) switch, set the temperature to the lowest, and turn on the external circulation to defog. Both cold and warm air can be used to defog the car windows, but warm air is slower than cold air. The most effective method is to use cold air, which blows dry cold air directly onto the glass, preventing water vapor from condensing on the glass and achieving the purpose of defogging. The method of using warm air to defog is the same as using cold air, but it should be noted that warm air should not be used on rainy days as it may initially worsen the fogging. When the car windows fog up, the external circulation should be turned on. The reasons for car window fogging: There is a certain temperature difference between the inside and outside of the car. If the temperatures inside and outside the car are different, the surface with the lower temperature will have a lower saturated vapor pressure than the surrounding environment, causing water vapor to gather on the glass surface and form tiny water droplets, resulting in fogging. Methods to defog car windows: Air conditioning cooling: Use the air conditioning's dehumidification function to reduce air humidity and remove fog. In summer, especially when multiple people enter the car and the air conditioning is not turned on in time, the exhaled air has high humidity, and the windshield will quickly fog up. At this time, you can turn on the air conditioning to blow cold air onto the windshield, using the dehumidification function to remove the fog quickly. If the humidity is too high and the air conditioning is not effective, you can slightly open a window to quickly reduce the humidity inside the car. Of course, combining this with the air conditioning will yield faster results. Air conditioning warm air: Use the method of reducing the temperature difference to remove fog. In winter, blowing warm air onto the glass can quickly raise the temperature of the windshield, reducing the temperature difference between the inside and outside surfaces of the window and preventing heavy fogging. However, it should be noted that the rear and side windows heat up more slowly, so it takes longer to remove all the fog. Whether the air conditioning is automatic or manual, turning it on helps with dehumidification. The temperature control should not be set to the coldest position, as this may cause the outer surface of the windshield to fog up over time. Applying anti-fog spray for prevention: Spray a small amount of anti-fog agent on the car windows and wipe it clean to remove dirt and stains. While polishing the glass, a thin transparent protective film is formed, effectively preventing water vapor from condensing on the glass and forming fog. This is especially useful in cold winters. Alternatives to anti-fog spray include dish soap, soapy water, glycerin, alcohol, or saline solution. After drying, wipe off any excess residue with a chamois or soft dry cloth to ensure the windows remain fog-free for several days. Opening windows for air circulation: If the fog inside the car is not too heavy, you can open the windows on both sides to create air circulation between the inside and outside of the car, reducing the temperature difference and allowing the fog to dissipate slowly. The principle of this method is the same as using cold air from the air conditioning. The downside of opening windows is obvious: it is not suitable during rain, snow, on highways, or when the fog is heavy. Rear window heating: Most cars have a rear window heating function, though the button location may vary. Turning on the rear window heating switch will remove the fog in about a minute. Turning on external circulation: On rainy days in spring or autumn, you can turn on the external circulation to blow air onto the windshield. Opening windows may not be suitable, and turning on the air conditioning may feel too cold. At this time, you can turn on the external circulation and adjust the air vent to blow onto the windshield, quickly lowering the temperature on the inner side of the windshield and making the fog disappear.

[MelanieDella]

I've been driving for over a decade, and encountering fog on the windshield is a common occurrence, especially during rainy days or winter. The main reasons are the significant temperature difference between the inside and outside of the car, coupled with high humidity. My approach is to immediately turn on the air conditioning's dehumidification mode or press the defrost button as soon as I get in the car, adjust the airflow direction to blow towards the windshield, and increase the fan speed to quickly clear the fog. If the fog is not heavy, I switch to recirculation mode to prevent moist outside air from entering; but if I feel difficulty breathing, I switch back to fresh air mode for ventilation. Safety comes first—never distract yourself by wiping the windshield while driving. When parking, I recommend clearing any debris on the windowsill to prevent moisture buildup. Developing a habit of checking the wipers and air conditioning system can reduce trouble, especially before long-distance drives, ensuring the interior stays dry and comfortable.