this is from Consumer report.org:
When looking to find a great price by shopping yard sales or searching online, be careful not to end up with a recalled item that is a safety hazard to you or your children. Don Mays, our product safety director, points out the following types of products to avoid buying used, because of their potential safety hazards.
Do not buy used:
Over the past several years, our marketplace has been flooded with poor-quality, mostly foreign-made, cribs that were a serious safety hazard to young children—particularly drop-side cribs. More than 11 million dangerous cribs were recalled between 2007 and 2010, according to the Consumer Protection Safety Commission. Drop-side cribs with detaching side rails were associated with at least 32 infant suffocation and strangulation deaths between 2000 and 2010. Additional deaths have occurred due to faulty or defective crib hardware. But new crib safety standards went into effect in June, and will stop the manufacture and sale of traditional drop-side cribs. In addition, the standards require stronger mattress supports, more durable hardware and rigorous safety testing. However, many older cribs can still be found for sale anywhere from flea markets to online auction sites.
2. Bicycle Helmets
Helmets deteriorate over time, as ozone and sunlight degrades the plastic. But most importantly, once a bicycle helmet is involved in a crash it will no longer offer the same level of protection as before. You have no way of knowing if a helmet was previously involved in a crash, so skip buying used bicycle helmets. If it comes down to saving money, know that you don't have to buy the most expensive helmet to be assured of its safety, cheap helmets offer the same protection.
3. Child Safety Seats
Like bicycle helmets, you have no way of knowing whether a used car seat was involved in a car crash. Child safety seats that have gone through a crash will not offer the same level of protection during a second vehicle crash. Older car seats may not have the latest safety features, or meet the most recent safety standards, and may have degraded over time. Plus, car seats carry an expiration date, typically six years.
4. Children's Outerwear With Drawstrings
Before buying, check all children's outerwear to make sure the garments do not contain drawstrings. Although there have been federal guidelines and an industry standard for more than 10 years now forbidding their sale, clothing with hazardous drawstrings continues to be sold on the second-hand market. Drawstrings are a strangulation hazard because they can get caught on playground equipment and in other places, like bus doors.
5. Toys (including jewelry)
Toys and children's jewelry must meet certain federal safety standards, including acceptably low levels of lead in their paint and underlying materials. Yet you have no way of telling how much lead might be in a piece of children's jewelry or toy that could end up in a child's mouth. This month, new federal regulations reduce the lead limit in toy's underlying materials and other children's products from 300 to 100 parts per million. Surface coatings, such as paint, have been limited to 90 ppm since 2009. But again, you have no way of checking whether a used toy or piece of jewelry contains high levels of lead.