Monsoon is in full swing and one thing that most drivers encounter these days while driving are foggy windows particularly when it’s raining.
Condensation occurs when a surface is cooler than the dew point temperature of the air next to the surface. At this temperature, the air next to the surface loses its water content by condensation. The condensation is what makes your car’s windows appear foggy. When there is fog on your windows, you can’t see clearly in all directions, thus it’s dangerous. So it’s extremely important to know how to make sure your windows are clear.
Depending on the temperature and the situation you will want to battle the condensation on your windows with different methods. Imagine a cool, rainy morning… The air inside your car is similar to the air outside your car- heavy with moisture. When you enter the car and close the door, before you even start the engine you start inhaling and exhaling. That first breath you exhale is full to the brim with water vapor – at body temperature and this air pressure, it literally can’t hold any more water.
When the warm, moist air from your lungs meets the cold, moist air already in the car, the air from your lungs cools down, which leaves the water vapor from your lungs with no place to go. The water vapor then condenses on the nearest and coldest surface, which in a cold car, is the cold windscreen in front of you.
How to defog car windows?
If you have air-conditioning in your car the best and fastest solution is to turn it on and set it to the car demister outlets. Air-conditioners cool your car on a hot day by removing water vapor from the air inside the car, which reduces the temperature of the air.
So operating your air-conditioner in rainy conditions will immediately start removing water vapor from your car, so that your warm, moist breath will disperse into the air inside the car rather than condensing on the windscreen.
Also it’s good to use the fresh-air mode with a/c instead of re-circulation to get rid of the moisture inside the cabin. You can also turn on the AC and the heater at the same time. The AC unit acts as a dehumidifier even when the system is heating the air.
Don’t have air-conditioning?
If you don’t have air-condition in your car of if it is out of order, use the car windscreen demister button without air-conditioning and the ventilation system will try to warm up the windscreen, by blowing warm air at it.
While less effective than air-conditioning, these solutions will work eventually because they force the water vapor to find another place to condense once the heated portion of the windscreen becomes warmer than your breath.
You might also want to try opening enough windows to ensure your warm, moist breath is unable to reach the windscreen. Only then use a piece of cloth, or anything absorbent to wipe the condensation off the windscreen.
Trying to see through fogged-up windows is a driving hazard, but with these tips you can help increase your driving safety.
A 3d animation professional with over 20 years of industry experience having served in leading organizations & production facilities of Pakistan, an avid car enthusiast and petrolhead with an affection to deliver writings to help shape opinions. Formerly written for PakWheels as well as major publications including Dawn. Founder of CarSpiritPK.com