How to Deal with Foggy Car Windows?

[IkerLynn]

Press the defogging button, turn on the air conditioning (A/C) switch, set the temperature to the lowest, and turn on the external circulation to remove fog. Both cold and warm air can be used to defog car windows, but warm air is slower than cold air. The most effective method is using cold air, which blows dry cold air directly onto the glass, preventing water vapor from condensing and achieving defogging. The method for warm air defogging is the same as cold air, but note that warm air should not be used on rainy days as it can initially worsen the fog. Always use external circulation when defogging car windows. The reason for foggy car windows: There is a temperature difference between the inside and outside of the car. If the temperatures differ, the side with the lower temperature will have a lower saturation vapor pressure, causing water vapor to condense on the glass surface, forming tiny droplets and creating fog. Methods to defog car windows: Air Conditioning (Cold Air): Use the air conditioning's dehumidification function to reduce air humidity and remove fog. In summer, especially when multiple people enter the car without turning on the AC, the high humidity from their breath can quickly fog up the windshield. Turning on the AC to blow cold air onto the windshield can dehumidify and remove the fog quickly. If the humidity is too high and the AC is ineffective, slightly opening the windows can rapidly reduce the cabin's humidity. Combining both methods can yield faster results. Air Conditioning (Warm Air): Use warm air to reduce the temperature difference and prevent fogging. In winter, blowing warm air onto the windshield quickly raises its temperature, reducing the temperature difference between the inside and outside surfaces and preventing heavy fogging. However, the rear and side windows heat up more slowly, so it takes longer to remove all the fog. Whether using automatic or manual AC, turning it on helps with dehumidification. Avoid setting the AC to the coldest temperature to prevent frost from forming on the outer windshield. Applying Anti-Fog Agents: Spray a small amount of defogging agent on the car windows and wipe it clean to remove dirt and stains. This leaves a thin transparent protective film that prevents water vapor from condensing, especially useful in cold winters. Alternatives to defogging agents include dish soap, soapy water, glycerin, alcohol, or saline solution. After applying, let it dry and wipe off excess residue with a chamois or soft cloth to keep the windows fog-free for several days. Opening Windows for Airflow: If the fog is light, opening the side windows can create airflow between the inside and outside of the car, reducing the temperature difference and gradually dissipating the fog. This method works on the same principle as using cold air from the AC. However, it has obvious drawbacks and cannot be used during rain, snow, on highways, or when the fog is heavy.