MADISON, Wis. -- The warm weather in the Madison area is a sign of many things: The school year is about to end, the Milwaukee Brewers are close to becoming mathematically eliminated from the playoffs and garage sales are as commonplace as road construction projects.

But there are some items that smart shoppers will think twice about before purchasing secondhand. Chief among them is buying child car seats.

Everyone loves a bargain, but putting a price on a child's safety is a bad idea, and experts say that is exactly what those who purchase car seats at a yard sale are doing.

Teresa Burkeland said she isn't looking to compromise anyone's safety. She's just looking to sell something she didn’t use much.

"I used it maybe four weeks," said Burkeland, about the car seat she's selling, "because we were watching a newborn."

Jennifer Moore also sold a car seat. She said she felt fine about it because she knew it was safe.

"I wouldn't want to sell a seat that I wouldn't want to buy myself," said Moore. "So, I try to make sure I have the manual with it and make sure it's not expired, make sure that the buckle and everything works, and it's safe."

Moore hints at a checklist that Sherri Faust of the Dean Foundation said is important that parents think about when purchasing a used seat.

"Families need to know the complete history of the car seat," said Faust. "And that includes how it was cared for, how it was used, how old it is, has it ever been involved in any kind of crash or collision."

Despite giving guidelines, Faust warns that a stranger should not necessarily be trusted, particularly with something as important as a child’s car seat.

"If you can trust who you're getting that used car seat from, you're OK to use it," continued Faust. "But if you don’t know that person, or the yard sale you're stopping by, you're better off getting a brand new one. You can't put a value on your child's life."

Experts say.that potential buyers of used car seats should always investigate when it was made.

The seats are only good for six years from the time they were produced. Car seats are regulated to have an expiration date imprinted on the seat itself.

For more information on child car seat safety, check out this page at the National Highway Traffic Safety Administration website.