Should You Use Internal or External Air Circulation When Driving in the Rain?
4 Answers
When driving in the rain, it is recommended to use external air circulation. Related information is as follows: 1. Removing Fog: If you want to completely eliminate fog inside the car, you should turn on the air conditioning and select the hot air setting to blow on the windshield. Similarly, start by using external circulation, choose the hot air setting and direct the airflow to the front windshield vents. Wait for about 5 minutes, then switch to internal circulation or simply turn it off. Using the air conditioning heating function for defogging will be faster and more effective. 2. Reason for Not Using Internal Circulation: With internal circulation, both side windows may fog up, affecting the driver's visibility. Therefore, it is best to use external circulation and adjust the airflow direction toward the windshield. Using external circulation helps to expel the moisture exhaled by passengers out of the car, while the outside cold air is less likely to condense.
When driving in the rain, I always prefer to use the external air circulation mode as it effectively prevents window fogging and ensures driving safety. As a veteran driver with over a decade of experience, I've learned the hard way from using internal circulation in rainy conditions—resulting in foggy windows and impaired visibility: high humidity inside the car, poor air circulation, and moisture condensing on the glass. Sudden fogging once nearly caused me to rear-end another vehicle. Switching to external circulation introduces drier outside air, and when combined with the AC's cool air or defogging function, it quickly clears the fog. Even if it gets stuffy after sitting in the car for a long time, I prioritize external circulation, only briefly switching to internal circulation for a few seconds when outside dust is excessive. But overall, safety comes first—never take it lightly.
I usually prefer using the external air circulation when driving in rainy weather, as it makes the car interior more comfortable and safer. I often drive my family out for trips, and during heavy rain, the air inside the car tends to get stuffy. Using internal air circulation would recirculate the humidity, causing the windows to fog up and obstructing the rearview mirror visibility. This forces me to frequently wipe the windows or open them, which is quite troublesome. With external air circulation, the airflow improves, reducing fogging, and the air conditioning helps with dehumidification and cooling. I remember one time on the highway during heavy rain—I forgot to switch to external air circulation, and the windshield became completely fogged up, startling me into quickly switching modes. I’ve remembered ever since. Depending on the season, extra attention is needed to prevent fogging during winter rain—just avoid setting the air conditioning temperature too high.
I prefer using the exterior air circulation mode when driving in the rain because the interior circulation increases the risk of window fogging. My car has a standard air conditioning system, and during heavy rain when humidity is high, I simply turn the knob to the exterior circulation button to let fresh air in and dry out the cabin. In the past, I tried using interior circulation, but the windows ended up foggy, blurring my vision and making driving stressful. Combining this with the air conditioning's cooling or defogging function speeds up the effect. For my daily commute, this setup gives me more peace of mind during heavy rain, preventing accidents caused by fogged-up windows. Safety is the top priority, so I personally recommend this approach for rainy days.
