Dangers of Fire in Cars in Hot Weather

Common Everyday Items That Can Become Fire Hazards in Cars

Here’s a breakdown of the most problematic items and what makes them so dangerous when left in a hot vehicle:

1. Disposable Lighters and Vapes

These small, often forgotten items are among the most dangerous.

- Lighters contain pressurised butane, which expands rapidly when heated. In extreme heat, they can crack, rupture, or even explode.

- Vapes and e-cigarettes contain lithium-ion batteries and often flammable liquids — a double threat. Overheating can cause battery failure (thermal runaway) or leakage, and the liquid may ignite.

2. Aerosol Cans (Deodorant, Cleaning Products, Paint, Air Fresheners)

Aerosols are sealed under pressure, and nearly all have a “do not store above 50°C” warning. In-car temperatures can easily exceed this. When the internal pressure builds up past the safety limit, cans may burst, releasing flammable gas or harmful chemicals.

3. Hand Sanitiser and Alcohol-Based Cleaners

These contain high concentrations of ethanol or isopropyl alcohol — both extremely flammable. In a sealed, hot environment, vapour can accumulate. If exposed to a spark, static discharge, or direct sunlight through a magnified lens, ignition is possible.

4. Pens

Many pens are made with thin plastic barrels and pressurised ink cartridges. In high heat, the ink can expand, leak, or even rupture the barrel. This can result in messy stains, damage to upholstery or electronics, and in rare cases, chemical fumes or flammable vapour depending on the ink type.

5. Power Banks and Lithium Batteries

Lithium-ion batteries are used in power banks, phone chargers, tablets, and other gadgets. High heat can cause the electrolyte inside to break down, leading to leaks, swelling, or thermal runaway.

6. Canned Drinks

Like aerosol cans, carbonated drinks are stored under pressure. Heat causes the liquid and gas inside to expand to bursting. While this may not cause a fire directly, it can create a sticky, corrosive mess that damages electronics, upholstery, and internal fittings — and could create a hazard if a driver is startled while entering the vehicle.

7. Petrol Canisters

Even small amounts of petrol in portable containers can release flammable vapours. In a hot, enclosed vehicle, vapour pressure increases significantly, posing a high risk of explosion or ignition, especially if the canister is not fully sealed or stored correctly.

8. Reading Glasses and Sunglasses

While not a flammable item, glass lenses left on the dashboard or seat can act like magnifying glasses, focusing sunlight into a narrow point. This can ignite flammable materials such as paper, tissues, seat fabric, or plastic components.

9. Plastics

Soft plastics can warp, melt, or emit fumes when exposed to extreme temperatures. Like the lenses of glasses, clear plastic bottles can also refract sunlight, potentially focusing heat onto flammable surfaces and increasing fire risk. There are documented cases of smouldering seats caused by sunlight through a half-full bottle left on the dashboard.

What Can Happen When These Items Ignite?

Vehicle Damage

Interior fires, whether small or extensive, can destroy dashboards, seats, and electronics. Smoke damage alone can render a vehicle undriveable. Replacing upholstery, repairing scorched dashboards, or cleaning up after an aerosol explosion can cost hundreds or even thousands of pounds or dollars.

Injuries and Safety Risks

In worst-case scenarios, these fire risks can lead to injuries — especially if a driver re-enters the vehicle unaware that an item is overheating, or if an object explodes during a drive. There’s also risk to passersby or nearby parked vehicles in densely packed areas.

Daily Clean-Out Routine

Get in the habit of removing high-risk items — especially lighters, vapes, aerosol cans, and batteries — at the end of each day or when the car will be idle for more than a few minutes.
Encourage family members or employees to do the same.

Store Smart, Not Hot

Keep necessary items in insulated bags or shaded compartments, and never leave flammable items on the dashboard or seats.
Use purpose-built storage cases for electronics and battery packs with heat-resistant liners.

Use Sunshades and Park in the Shade

Reflective windscreen sunshades can drastically lower dashboard temperatures.
Parking in covered or shaded areas reduces heat exposure, especially during peak sunlight hours.

A Few Minutes of Prevention Could Save a Car — or a Life

It’s easy to overlook the things we leave behind in our cars — a vape in the cupholder, a can of deodorant in the glovebox, a power bank under the seat. But when summer arrives, those everyday items need to be top of mind when exiting the vehicle.