be less effective and that changing laws and regulations necessitate an expiration date. Opponents argue that it is simply for their legal protection and to sell more car seats, and point out that manufacturers have noted that the plastics in most car seats long outlast the expiration date. As ageing is due to temperature swings and UV-light, a seat ages faster in a car than in a cool, dark cellar. Like motorcycle and race car helmets, child restraints are tested for use in just one crash event. This means that if the restraint is compromised in any way (with or without the child in it), owners are strongly suggested to replace it. This is due to the uncertainty with how a compromised child restraint will perform in subsequent crashes. The National Highway Traffic Safety Administration (NHTSA) provides guidance on the reuse of child restraint systems after a crash. Replacement of child restraints is recommended following a moderate or severe crash in order to ensure a continued high level of protection for child passengers. However, recent studies demonstrate that child restraints can withstand minor crash impacts without any documented degradation in subsequent performance. A minor crash is defined by the NHTSA as one in which all of the following apply: A visual inspection of the child safety seat, including inspection under any easily movable seat padding, does not reveal any cracks or deformation that might have been caused by the crash The vehicle in which the child safety seat was installed was capable of being driven from the scene of the crash The vehicle door nearest the child safety seat was undamaged There were no injuries to any of the vehicle occupants The air bags (if any) did not deploy Crashes that meet all of these criteria are much less severe than the dynamic testing requirement for compliance with Federal Motor Vehicle Safety Standard (FMVSS) 213 and are highly unlikely to affect future child safety seat performance. Child restraints are sometimes the subject of manufacturing recalls. Recalls vary in severity; sometimes the manufacturer will send an additional part for the seat, other times they will provide an entirely new seat. The purchase of a used seat is not recommended. Due to the aforementioned concerns regarding expiry dates, crash testing, and recalls, it is often impossible to determine the history of the child restraint when it is purchased second-hand. Children traveling by