She writes: “It is extremely dangerous for families to get their children’s car seats at flea markets, second hand shops, yard sales, Freecycles, etc. There is no way to know for sure if the car seat has been in a crash, if the straps have been machine washed, or if it is missing pieces. All of these things increase the risk that the child will suffer permanent serious or even fatal injury in a crash!”
She recommends donating them to a local child passenger safety technician for training purposes. Search for a good place at seatcheck.org.