Should You Use Cold or Hot Air to Defog Car Windows?

[DelRonan]

Both cold and hot air can be used to defog car windows. Reasons for window fogging: Excessive temperature difference between inside and outside. The external temperature is high, resulting in a higher saturation vapor pressure of water vapor, while the car window glass temperature is low, leading to lower saturation vapor pressure near the glass. When water vapor condenses on the glass surface, fog forms. To defog, it's necessary to maintain consistent temperatures inside and outside the vehicle. Usage scenarios for defogging: Using cold air for defogging can quickly dry the moisture on the windshield. Therefore, cold air is suitable for emergency defogging while driving. However, using cold air for defogging in winter can make drivers and passengers uncomfortable. Using warm air for defogging will initially increase fogging on the glass, but the fog will gradually dry out over time with the warm air. It is not recommended to use warm air for defogging while driving.