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PITTSBURGH (KDKA) – You know the safest place for your child in the car is in a car seat. However, you may not know that car seats expire.

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Millions of outdated car seats may be in vehicles across the country right now.

Samantha Booth knows the right thing to do when it comes to her three children and her car.

All of her children are safely buckled into car seats. But, what Booth didn’t know until recently is that car seats expire.

She was shocked when she realized that the car seat she had handed down from her son to her daughter to another son was expired by the time she put her third child in it.

“I had no idea. I felt really guilty that it had been expired for a year when he was in it,” says Booth.

(Photo Credit: KDKA)

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Most car seats expire after six years.

“When you look at car seats they are made with a lot of plastic. That plastic starts to break down or degrade over time,” says car seat expert Kristen Urso, with the American Academy of Pediatrics. “That seat may not hold up the way it’s supposed to.”

To find the expiration date on a car seat, you need to look for a sticker usually located on the bottom of the seat. There, you will find the serial number along with the “manufactured” date and the “do not use after” date. If the seat is expired, experts say you need to get rid of it.

“Even if we are not seeing wear and tear, the damage is possibly there,” says Urso.

According to Safe Kids Worldwide, three out of four car seats are being used incorrectly, which includes car seats that are expired.

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Correctly used car safety seats can reduce the risk of death by as much as 71 percent.

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If you do have a car seat that is expired, experts say throw it away. You should cut the straps and the fabric so someone else can’t take the seat and use it after you toss it. And, you should avoid buying or selling car seats at garage sales.