A viral-style warning claims that a simple water bottle left inside a hot parked car can become dangerous. It says firefighters have shown that clear plastic bottles can focus sunlight like a magnifying glass, potentially damaging car interiors or even starting fires in extreme conditions.
The idea is that sunlight passing through a water-filled bottle can concentrate into a small beam of heat. If that beam lands on flammable materials like upholstery or clutter, it could, in rare cases, cause scorching or ignition, especially inside a very hot, closed vehicle.
