We all know the kind of things that we need to have at hand on : sunscreen, sunglasses, a hat and a big bottle of water to keep you hydrated. But did you know that one of these essentials could spell disaster if you leave it in your car? Yes, it’s time for a quick Jalopnik health and safety lesson after one Reddit poster uncovered in their car on a sunny day.

The poster, WarningImBroken, to share the disaster that befell them when they left a water bottle in their car. They posted “Today I learned not to leave a clear bottle of water in my car on a hot sunny day!!” accompanied by two images of the smoldering remains of their car.

It’s a rough sight, with the wheel melted out of shape, and all manner of metalwork exposed after losing its flammable surroundings.

At first, blaming such a singed wreck on the water bottle seems like a pretty dramatic leap. But how often being caused by glass bottles being left around the wilderness? In the wilderness, the glass magnifies the light of the sun onto the dried out ground, which can spark a fire.

The same principle applies to water bottles when they are left in your car. A clear bottle filled with water acts as a magnifying glass, which can concentrate the sun’s rays onto a spot on your interior and, if you’re really unlucky, .

That appears to be what’s happened to this Redditor, and it’s a phenomenon that fire departments have repeatedly warned about when the warmer months roll in.

The Midwest City Fire Department even took to YouTube to highlight the dangers. In the video (linked above), the MCFD demonstrated how a clear bottle can ignite a piece of paper, and warned that they could do the same with other dry, flammable materials.

So, while we’re clearly not saying don’t take water out on the road with you, maybe swap out the clear plastic bottle you might buy in the store for an opaque reusable bottle. Or, remember to take your bottle with you whenever you hop out from the driver’s seat. The more you know.