Why is there water vapor in the car headlights?

[Monica]

Here are the specific reasons for fogging in headlights: Excessive heat: During the use of headlights, a significant amount of heat is generated. To ensure normal operation, the car expels this heat as much as possible through a venting rubber tube. However, moisture in the air can easily enter the headlight through this tube and adhere to the lens. As the moisture accumulates, water droplets form and flow down the lens. Engine compartment water accumulation: When using a high-pressure water gun to clean the engine compartment, owners often forget to promptly remove the accumulated water. After closing the engine hood, the moisture cannot quickly dissipate outside the vehicle, remaining trapped in the engine compartment, which may then enter the headlights. During seasons with frequent thunderstorms, it is advisable for owners to develop a habit of regularly checking their vehicle lights.