It's difficult -- and unsafe -- to drive when your car windows are fogged up. This generally happens when the temperature of your windows is cooler than the dew point within your car's cabin. As a result, moisture vapor in the air (humidity) settles on the windows, causing them to fog up. Basically, there's too much moisture in the air, which causes it to condense on the glass windows. So, how do you keep your car windows clean and fog-free?
Turn on the Defroster
Perhaps the easiest and most effective solution to treat fogged windows is to turn on the defroster. Defrosters are designed specifically for removing frost, and subsequently, moisture. Therefore, turning on your front and rear defrosters can help eliminate condensed moisture on the windows.
Additionally, you can give a helping hand by turning on your car's air conditioner. The air conditioner will dehumidify your car's interior more quickly than the heater. So, when used in conjunction with the defrost, this is an effective way to eliminate fog from your windows.
Don't Recirculate the Air
While both the air conditioner and heating can eliminate moisture from the air, the former is more effective. With that said, you should set your car's air conditioner to bring in fresh air from outside. Most automotive air conditioning systems have two settings: recirculate or fresh air. The recirculate setting will simply recirculate the air that's currently inside your car's cabin, whereas the fresh air setting brings in air from outside. For the purpose of defogging windows, the recirculate setting is more effective.
Another idea is to keep a demister pad in your car. When the windows become fogged up, run the pad across them. Demister pads are particularly effective for this purpose because of their moisture-absorbent properties. They absorb and hold moisture better than most other materials, allowing you to see more clearly through your car's windows.
You might be surprised to learn that there are products available to keep windows fog-free. Known as "anti-fog coatings," they create a barrier of protection between your car's windows and the outside air.
With anti-fog coatings, however, there are a few things to keep in mind. First, they only offer temporary protection and must be reapplied regularly. Secondly, some anti-fog coatings themselves can restrict visibility through the window. Therefore, it's important to choose the right type of anti-fog coating.