South Yorkshire Safer Roads Partnership
News
03 Dec 2020
DE-MISTING YOUR WINDSCREEN
Demisting your windscreen is a necessity before setting off, not doing so can impede your vision while driving which means you will be driving illegally.

Here's how to clear your windscreen in double-quick time:

1. Use the heater (correctly)

Start the heater off cold, then slowly increase the temperature as the air dries out, rather than overloading the cabin with hot, ‘wet’ air.
Try to find a temperature and humidity that’s comfortable but doesn’t mist up the cabin.
Make sure your heater's blast is directed at the windscreen and the windows - the warmer air (even on cold the air will be warmer than the ice cold windscreen) will dry the glass a little through evaporation and begin to heat up the glass to stop the water vapour condensing on it again.
Of course, if you're not in a rush and your frozen bones need warmth then use the hot air to warm both you and the windscreen.
It may take a little longer to clear fully but you will at least be a little more comfortable - just don’t move off until all glass surfaces on your car are clear. It’s dangerous and illegal if visibility is impeded.

2. Use the air-con if your car has it;

If your car has air-conditioning make sure it is switched on.
Use the air-con in conjunction with the heater. Hot air will dry the glass a little through evaporation, but the air will then cool down and condense on the glass once more, so make sure the air-con is on to keep the atmosphere inside dry.
If your windscreen is iced over, then the heat is obviously more necessary. But in this instance you might want to scrape the outside of your windscreen clear first.

3. Use your windows:

If you don’t have a clever climate control system, having the windows down could actually help clear the screen faster.
This helps because the dry, cold air from outside can help reduce the amount of water vapour inside the car, stopping the screen misting up.
Then you can begin to warm the car up gradually to a temperature that suits you after you have cleared the windscreen. 
Of course, you should never pull away with your vision impaired, but if your windows start to mist up during driving this is also a worthwhile tactic, for those without air-con. If the misting clouds too much of your vision you should pull over where safe to do so and wait for your windows to clear

4. Use your climate control system:

If you do have a clever climate control system, utilise it. There’ll most likely be a setting for demisting the windscreen, which will automatically adjust the ventilation system’s parameters to achieve the best results. 

For more on this subject visit: https://www.rac.co.uk/drive/advice/winter-driving