Despite the milder temperatures the UK is currently experiencing, the mornings are still off to a chilly start. Whether you’re doing the school run, or commuting into work, if you’ve been getting in the car in the morning, you might have noticed your windscreens fogging up. 

Cars can feel particularly chilly first thing in the morning after they’ve been out in the cold all night, and switching your heat on is typically why windscreens fog up. But it can also simply be from our own body heat entering the car. It’s illegal to set off on a drive without a clear view of the road, and it’s not just windscreens that fog up - the rear window can also become misty as a result of condensation. Cracking a window can help with both of these problems, but there’s also buttons for this. 

Many drivers, however, don’t realise the crucial difference between the buttons, and improper use of them could result in penalty points, or a fine of up to £2,500, as driving with misty windows can prevent you from being able to see vehicles and pedestrians. 

The Highway Code rules that drivers must have a clear view of the road, and knowing the difference between the demist buttons on your dashboard could be life-saving. 

Graham Conway, managing director at Select Car Leasing, said: “It’s astounding how many people get behind the wheel without really knowing what everything in their car means or does.

“We see it all the time with demisting buttons. A lot of drivers don’t know the difference between the front and back window buttons, which can be very dangerous.”

The two buttons have different functions depending on which window is fogged up, meaning both should be used as intended. To demist the front windscreen, drivers need to be using the button with a curved rectangle and three squiggly lines running through it.

This activates the vehicle’s air conditioning system to direct warm, dry air onto the windscreen, helping clear internal condensation and clearing the window. 

The rear demist button has a rectangle and three squiggly lines running through it, and uses heating elements embedded in the rear window to get rid of any condensation or frost in the colder months. 

"Misunderstanding these controls can result in drivers struggling with misted or foggy windows, significantly increasing the risk of accidents due to reduced visibility,” said Graham. 

A critical safety issue, Graham also recommended drivers always familiarise themselves with their vehicles, and ensure their vehicle’s heating and ventilation system is well-maintained to avoid any issues with demisting. 

Dirt and grime can also make condensation problems worse, so regularly cleaning your car will ensure the demisting systems remain effective.