What are the solutions for car window fogging?

[OPatrick]

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 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 defogging. The method for using warm air is the same as cold air, but note that warm air should not be used for defogging on rainy days, as it may initially worsen the fogging. Always use external circulation when defogging car windows. The reason for car window fogging: There is a temperature difference between the inside and outside of the car. If the temperatures inside and outside 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 droplets, resulting in fog. Methods for defogging 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 promptly, the high humidity from exhaled breath can quickly cause the windshield to fog up. In this case, turn on the air conditioning to blow cold air onto the windshield, utilizing the dehumidification function to quickly remove fog. If the humidity is too high and the air conditioning is ineffective, slightly open the windows to rapidly reduce the humidity inside the cabin. Combining this with the air conditioning can speed up the process. Air conditioning warm air: Use warm air to reduce the temperature difference and remove fog. In winter, blowing warm air onto the windshield quickly raises its temperature, reducing the temperature difference between the inside and outside surfaces of the glass and preventing heavy fogging. However, note that the rear and side windows heat up more slowly, so it takes longer to completely remove fog. Whether using automatic or manual air conditioning, turning it on helps with dehumidification. Avoid setting the temperature to the coldest, as prolonged use can cause fogging on the outside of the windshield. Applying anti-fog spray or other preventive measures: 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 on the glass, effectively preventing water vapor from condensing and forming fog, which is especially useful in cold winters. Alternatives to defogging agents include dish soap, soapy water, glycerin, alcohol, or saltwater. After applying and letting it dry, wipe off any excess with a chamois or soft dry cloth. This can keep the windows fog-free for several days. Opening windows for air circulation: If the fog inside the car is not too heavy, opening the side windows can create air circulation between the inside and outside, reducing the temperature difference and gradually dissipating the fog. This method works on the same principle as using cold air from the air conditioning. However, it has obvious drawbacks and cannot be used during rain, snow, on highways, or when the fog is too 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 usually clear the fog in about a minute.