MIAMI (CBSMiami) — Hand sanitizer is important to keep around, but you might not want to keep it in your car on a hot day. That’s because flammable liquids and direct sunlight can make it explode, warns a Wisconsin fire department.

The Western Lakes Fire District explains most hand sanitizers are alcohol-based, making them flammable.

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It posted a photo showing a burned out car door “resulting from contact with open flame.”

It clarified the post saying if sunlight refracts through the clear bottle in the right way, it could cause the gel to ignite. The department was using the picture as a reminder that hand sanitizer is flammable.

It did not say the fire in the picture was caused by an exploding hand sanitizer bottle, but wants people to be aware that it can by a fire hazard.

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When hand sanitizer is wet on any surface it will ignite when exposed to flame,” said an updated Facebook message.

Experts also say pump bottles pose a greater risk because vapors can leak into a hot car and create a combustible environment.

There are also concerns that leaving hand sanitizer in a hot car could make it less effective because if the alcohol evaporates, the hand sanitizer is less efficient. It is the alcohol that kills the germs.

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The best advice experts have to offer is to simply carry the hand sanitizer with you.