Here's how keeping bottled water in a hot car starts fires

The feeling of getting inside a car parked in the sun isn’t a pleasant one for drivers.

Thursday, 22nd July 2021, 9:32 am
Updated Thursday, 22nd July 2021, 9:34 am

But what some motorists don’t know, is that the heat build up in a car’s interior can cause damage to a manner of everyday objects.

When the sun’s energy enters the car and begins to heat solid objects, it begins to create what is called a greenhouse effect.

Studies have found that an outdoors temperature of 22°C can cause a carto heat up to 47°C in the space of an hour. When objects are left in such a stifling heat it can cause damage to them and potentially your car.

It’s commonly known that warming a plastic bottle causes chemicals such as Bisphenol A and phthalates to be released in to water when left in a warm environment for a sustained period of time.

It’s commonly known that warming a plastic bottle causes chemicals such as Bisphenol A and phthalates to be released in to water when left in a warm environment for a sustained period of time.

However, Select Car Leasing also found that water bottles left in cars in summer pose as a fire risk.

Plastic and water filters light just like a magnifying glass, which can concentrate the sun’s rays into an energy beam that can burn your fabric car seats.

Other objects that you should never leave in a hot car are:


Suncream can become less effective if left in a hot car. Sun cream bottles have been known to explode in warm environments. Not only can theplastic warp it’s shape in a high heat, warming the cream can actually alter the shelf life, meaning you could be going without valuable UV protection and risk damaging your skin.


A warm vehicle will make medicine less effective. Tablets can also be less effective when kept in a warm environment. Plastic capsules can change shape and regular tablets can even have an impact on the efficiency of them edication that you’re taking.

The NHS website advises that most medicines are to be kept in a cool, dry place unless otherwise stated.

Mobile phones

Heat can cause irreparable damage to your mobile phone. Gadgets like iPads, mobile phones and other tablets are not only a target for thieves but they’re also vulnerable to heat.

Leaving battery powered devices in a hot car can permanently damage the gadgets internal components, causing the miniature circuit board to flex and warp the battery. It can also damage screens, causing them to pixelate, crack and become unresponsive.


Soft drink cans can burst and spill. Even when not left in direct sunlight, heat applied to compressed cans of soft drink can cause them to explode. Although it is little more than a nasty mess when parked, it could cause enough of a distraction to cause an accident whilst driving.

Deodrant cans

Deodorant cans will explode if left in a hot car. It’s best practice to take any aerosol cans out of your car when it’s getting warmer. A study found that if it is 22°C outside, it can reach up to temperatures of 47°C within the space of an hour inside a car. An environment that hot can cause the pressure inside the cannister to increase and potentially cause an explosion.


Makeup can breed harmful bacteria in heat. Just like food, make up can go bad when heat is applied. A warm environment will not only cause some of your favourite beauty items to melt, it’s also a breeding ground for harmful bacteria to grow.

Graham Conway, General Manager at Select Car Leasing, recommends avoiding direct sunlight where possible when parking.

He said: “In the UK, it’s easy to overlook the dangers of leaving objects in ourcars in summer, especially when you think other countries experience much warmer weather, but that does not mean there’s no risk.

“Parking in the shade will best protect your car, and its contents, from the summer sun. If you do happen to leave any vulnerable objects in your car when you’re out on a journey, store the items in your glovebox or in your boot so they’re out of direct sunlight until you reach your destination."