Should You Use Cold or Warm Air to Defog the Car?

[DelParker]

Both cold and warm air from the car's air conditioning system can be used to remove fog. Using warm air to blow hot air onto the glass quickly raises the temperature of the front windshield, reducing the temperature difference between the inner and outer surfaces of the glass, thereby eliminating fog. Using cold air to defog is fast and direct, but prolonged use of cold air can make passengers uncomfortable. Methods to defog the car: 1. When the fog is not heavy, slightly opening both windows to allow air convection can eliminate the temperature difference on both sides of the windshield, making it difficult for fog to form. 2. Turning on the cold air can quickly remove fog in a short time. 3. Using warm air from the air conditioning can fundamentally solve the fogging problem. The fog will not return after turning off the warm air, nor will it make passengers feel colder in winter. 4. Applying a defogging agent on the windshield forms a protective film that prevents condensation.

[AliyahLee]

I usually drive to work and often encounter foggy windows, especially in the morning when the humidity is high. The first thing I do is turn on the cold air by pressing the AC button on the air conditioner, setting the fan speed high, and directing it towards the windshield. The cold air quickly condenses the moisture in the air, making the fog dissipate faster. If I only turn on the hot air, although it can dry the fog eventually, it might make the fog worse at first, which is really frustrating. I’ve also found that keeping the air circulation in external mode helps—avoid using internal circulation to prevent the air inside the car from getting more humid. In winter, if it’s too cold, I switch to hot air to warm up once the fog has reduced. Remember to check the air filter regularly; if it’s dirty, the dehumidification effect will be poor. Safety comes first—poor visibility while driving is dangerous. In short, cold air is quick and efficient for handling foggy windows.

[LaElizabeth]

Cold air or hot air? I've been driving for over 20 years and tried various methods. Generally speaking, cold air defogs faster, especially in hot weather or rainy seasons. The principle is simple: cold air lowers the windshield temperature, causing moisture to condense into droplets that flow away. Hot air, on the other hand, slowly dries the windshield, making it more comfortable in winter without the chill. But don't rush to turn on hot air—it might initially increase fogging when starting the car, affecting driving. I recommend using cold air first, then switching to hot air once visibility improves. Also, use the fan to speed up the process and wipe away minor fogging with a cloth. When humidity is high during rainy days, using the external air circulation to bring in fresh air works much better than recirculating cabin air. Regularly cleaning the interior windshield is also crucial, as dirt accelerates fogging.

[VonJune]

Foggy conditions? I prioritize turning on the cold air. When visibility gets blurry while driving, immediately press the AC button on the air conditioning and switch to defog mode. Cold air quickly removes moisture, clearing the fog. Hot air works too, but it's slower. Experience tells me that cold air works best on sunny days or right after rain; if the outside temperature is low, I wait a few minutes before switching to hot air to avoid constant adjustments. Meanwhile, set the fan to maximum speed to ensure airflow is directed at the windshield. Avoid using recirculation mode—opt for fresh air intake to prevent stuffiness. In short, cold air first, hot air as backup—drive safely.