Why is there fog in the car when it hasn't been driven?
4 Answers
Fog forms in a stationary car due to the temperature difference between the inside and outside of the vehicle. The amount of fog depends on the extent of this temperature difference. Hazards of fog in a car: 1. Interference with driving: Fog in the car can obscure the driver's vision, causing significant interference with driving. 2. Increased risk of accidents: In winter, cars are particularly prone to fogging. According to data from the National Ministry of Transport, winter accounts for 39.62% of annual traffic accidents, with poor visibility and bad road conditions contributing to half of these winter accidents. The fatality rate in winter traffic accidents is also notably higher.
Fogging occurs when the car is not in motion, primarily due to the temperature difference and humidity between the inside and outside of the vehicle. For instance, this morning I noticed my car windows were completely fogged up. Upon reflection, the high humidity inside the car could be due to the previous day's rain, leaving some moisture inside, or the carpets absorbing water. During the night or early morning, when the external temperature drops sharply, the cold surface of the windows comes into contact with the warm, moist air, causing water vapor to naturally condense into tiny droplets, forming what we call fog. This is not a mechanical fault but purely a physical phenomenon. Cars parked in garages tend to fare better, but those parked outdoors are more susceptible during seasonal changes. I regularly check the interior ventilation and ensure the car is dry before closing the windows, which also helps prevent subsequent issues like mold. If fogging accumulates too much, simply wiping it with a dry cloth or cracking the window slightly for ventilation can quickly resolve the problem.
Oh, I've encountered this situation several times—the car hasn't been moved for days, and the windows get foggy. The reason is actually quite simple: the car isn't running, but the air inside isn't idle. For example, when the weather turns cooler or after rain, the humidity inside the car rises. With a significant temperature difference, moisture condenses on the glass, forming fog. This is also related to the parking environment; if you park in a poorly ventilated area or near water, humidity builds up faster. I've improved my habits by clearing out umbrellas or wet items when parking and placing silica gel drying boxes near the dashboard, which works well. Excessive fogging isn't just an eyesore—over time, it can lead to mold growth, affecting health. So don't overlook these everyday details—prevention is always better than wiping the windows afterward.
Fog forming when the car is not in use is indeed common, and my car often experiences this when parked in the yard. The core reason is humidity condensation caused by temperature changes—simply put, fog appears when warm air cools down. It might be because you forgot to close the windows, or the external climate cooled down too quickly. This isn't a big issue, but it needs to be addressed. Regular ventilation is key.
