Summer heat can quickly turn a parked vehicle into a dangerous environment. Fire safety tests show that a clear plastic water bottle left inside a car may concentrate sunlight and generate enough heat to ignite nearby materials within just 10 minutes. Drivers are advised not to leave light-focusing or heat-sensitive items inside parked vehicles.

One vehicle fire in Huatan Township, Changhua County was traced to a clear plastic water bottle left on the dashboard. Over the past three years, Changhua has recorded five vehicle fires caused by the magnifying effect of transparent objects or overheating items such as lighters and lithium batteries.

Firefighters found that after about 20 minutes under the summer sun, seat temperatures reached 60°C while dashboards climbed to 88°C. Under the right conditions, a clear water bottle raised local temperatures above 115°C, confirming it can create enough heat to start a fire.

Besides clear plastic water bottles, objects such as glass bottles, magnifying glasses and crystal ornaments may also concentrate sunlight. Mobile phones, power banks, lighters and aerosol products can overheat or ignite when left inside a hot vehicle.

To reduce fire risks, drivers should park in shaded or underground areas whenever possible, use sunshades and check the vehicle before leaving. Removing light-focusing and heat-sensitive items can help prevent vehicle fires.