How to Deal with Fogging on the Car Windshield?

[Victor]

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. You can use either cold or warm air to defog the car windshield, 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 for using warm air to defog is the same as using cold air, but it should be noted that warm air should not be used for defogging on rainy days, as it may initially worsen the fog. When the car windshield fogs up, always use external circulation. The reason for fogging on car glass: 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 fog. Methods to defog car glass: Air Conditioning Cooling: Use the air conditioning cooling and dehumidifying 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 dehumidifying function of the air conditioning to remove the fog on the windshield quickly. However, if the humidity is too high and the air conditioning is not effective, you can slightly open the window to quickly reduce the humidity inside the cabin. 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, use warm air to blow hot air onto the glass, quickly raising the temperature of the windshield and reducing the temperature difference between the inside and outside surfaces of the glass. This can prevent excessive fogging on the windshield in time. However, it should be noted that the rear and side windows heat up more slowly, so it will take longer to remove all the fog. Whether the air conditioning is automatic or manual, turning it on helps with dehumidification. Do not set the air conditioning temperature to the coldest position, as this may cause the outer surface of the windshield to fog up over time. Spraying Anti-Fog Agents for Prevention: Spray a small amount of defogging agent on the car window and wipe it clean to remove dirt and stains from the glass. While polishing the glass, a thin transparent protective film is formed on the glass, which can effectively prevent water vapor from condensing and forming fog, especially suitable for cold winters. Alternatives to defogging agents include dishwashing liquid, soapy water, glycerin, alcohol, or saltwater. After applying, let it dry and then wipe off any excess fibers with chamois or a soft dry cloth. This can ensure the car glass remains fog-free for several days. Opening Windows for Airflow: If the fog inside the car is not too heavy, you can open the windows on both sides to create airflow between the inside and outside of the car, reducing the temperature difference and allowing the fog to disappear slowly. The principle of this method is the same as using cold air from the air conditioning. The downside of opening windows for airflow is very obvious: it cannot be used during rain, snow, on highways, or when the fog is heavy.

[JaylaRose]

In winter mornings, the windshield often fogs up, and I used to encounter this situation frequently. Don't panic when this happens. The first thing to do is to pull over to a safe spot, then slightly open the windows to allow air circulation. The fog will dissipate once the temperature difference between the outside wind and the inside decreases. You can turn on the heater or air conditioner, adjusting the airflow direction to blow onto the front windshield. Most cars have a button for this—just press it. If the fog is too thick, you can wipe the inside of the glass, but avoid distractions while driving as it's unsafe. I've tried using a mixture of dish soap and water on the glass, which can reduce fogging, but it's best to use a dedicated defogging spray. Regularly cleaning dust from the glass is also important, as dirt makes fogging more likely. Remember, safety comes first—don’t drive recklessly to save time. If visibility is poor, pull over and deal with it. Try to talk less when the windshield fogs up, and avoid breathing directly onto the glass.