Plastic Water Bottles Left In The Sun Could Set Your Car On Fire - Here's How

Here's a common situation for you: you're out on the road on a hot day with a big ol' water bottle in one hand. It's important to stay hydrated when the sun's bearing down and all that. At some point, you pull over somewhere, maybe for a few minutes, maybe for a little while, and you leave the water bottle in your car. Here's where things take a turn — you return to your car after your little outing to discover a smokey fire and the distinctive smell of car seat leather. How the heck does something like that even happen?

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As it turns out, the key to this fire, ironically enough, is that water bottle you left in your car. While the odds of this happening are very low, it's not an impossible event. If all of the correct factors align, it is possible for the water bottle to concentrate heat onto a focused point of your car. Ideally, this focused point wouldn't be a flammable material, or it would only make a small divot, but in the worst case, that intense heat could cause the softer parts of your car — like the seat — to catch fire.

How to prevent a water bottle fire

A water bottle-induced car fire requires a set of extremely specific circumstances to occur. Firstly, it needs to be a very sunny day, the kind of sunny day that makes your steering wheel so hot that you can't even touch it. Secondly, there needs to be a plastic water bottle somewhere in your car where the sunlight can reach, such as in the passenger seat. Third, the bottle needs to be clear, and full of a clear liquid like water.

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If all of these conditions coalesce and you're especially unlucky, the sunlight will pass through the clear plastic of the bottle and become magnified by the water, which functions like a lens. That magnified light focuses on a singular point, reaching temperatures of over 400 degrees Fahrenheit. If that point is made of flammable material, it could ignite. Have you ever seen a kid trying to set an anthill on fire with a magnifying glass? It's the same thing.

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So, how do you prevent this from happening? Simple: don't leave full water bottles in your car. If you absolutely need to leave a bottle in your car, try to leave it somewhere out of direct sunlight, like on the floor, or cover it with something solid like a hat.

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