Video simulating car accidents with child-sized crash dummies is frightening, and yet the result is what happens to children every day on U.S. roads.Car crashes kill five children each day, according to transportation officials."Children are very light, just like having a ball in a vehicle," said California Highway Patrol officer Paula Todd.Officials said another 640 children are injured in car crashes daily.The National Highway Traffic Safety Administration said the deaths and injuries are often the result of not securing a child in appropriate child safety seats.Todd said, "If you're involved in a crash, the child would actually fly just like a rocket."The child seats have proven so effective that they are mandatory in California.They are required in your own car and even a car you rent.Car rental agencies must make them available to parents like Debbie Dubrow.Dubrow is well-informed about safety seats so she was surprised by what she found after flying from Seattle to Lindbergh Field."We went down to San Diego on a family vacation and we had reserved a car with Advantage Rent-A-Car. We had also reserved two car seats with it," said Dubrow.The family went to the Advantage location on India Street where they had to pick out child safety seats from a back storage room."And some of the car seats had like cracker crumbs in them, black marks all over them. Several of them were just clearly broken," said Dubrow.According to the California Vehicle Code, car seats must be "in good and safe condition, with no missing original parts, not older than five years old."Dubrow complained to the Advantage manager."He just offered to refund the money that we had paid for the car seats and that was it," she said.That was not enough for Dubrow. She did not want other families using unsafe seats.So, Dubrow contacted 10News Investigates.Investigative producer Felicia Kit went to the same Advantage location to confirm Dubrow's allegations."We reserved a car and indicated we wanted to reserve some car seats," said Kit.An Advantage agent led Kit to the car seats in the same back room Dubrow described."I was kind of surprised. A lot of them were really dirty," said Kit.Kit paid for the car and $10 additional for each of the four car seats: an infant seat, two convertible seats and a backless booster seat. The seats were then taken to CHP officer Todd."It's a hazard to the child just due to the physical bacteria that's on the seat," Todd said.Todd found only one of the four rented seats -- the infant seat -- to be legal, and the legal seat was filthy."This particular tray and this particular tray are no longer in use," Todd said as pointed to the two convertible car seats.One of those seats was not only 7 years old, but it was also missing a vital part.Todd said, "It's missing the routing clip."The routing clip is a clip that holds the strap into the chair.Plus, the straps are so stiff and soiled, they can't be properly tightened -- they can't be made tight enough to protect the child's spine in an accident.The backless booster rented had a manufacturer's sticker that was torn."So, you're unable to even know anything about the seat as far as the model number to check for any recalls," said Todd.But by far the worst seat was the Fisher-Price car seat that was built in 1990.Todd said, "It's just not safe."The investigations team also swabbed the seats and sent the samples to a lab. One sample came back contaminated with light fecal matter.The team took its findings to the Advantage manager.Off-camera, manager Cavan Cox said he does not have any old car seats and that they are all in good shape. He admitted he hasn't gotten rid of any seats in two years.When the investigations team pulled out the pictures of the car seats rented to prove they were old, broken and dirty, Cox thanked 10News and said he would go through his supplies and would get rid of any unsafe or old car seats.The investigations team contacted the Advantage corporate office.A spokesperson guessed that what was found was isolated, but the team knew otherwise because as these seats were rented in San Diego, 10News' sister station in Seattle did the same at an Advantage Rent-A-Car location there and found a seat that was 8 years old, moldy and broken.The manager of the Seattle location was also unwilling to speak on camera.The corporate office did take action, sending a statement to 10News and adopting a new car seat policy.What should traveling families do?Todd said to play it safe by taking a personal child safety seat when traveling.Car seats are considered essential baby items so many airlines will not count them as an extra piece of checked luggage.