Child Resistant Closure Performance Aging Study

Child poisoning has been dramatically reduced by the introduction of child resistant (CR) closures on some common home chemicals and pharmaceuticals. However, “child resistance” (often mischaracterized as “child proof”) is a mechanical design property that is neither well understood nor supported by a body of theory, nor that can be specified from engineering first principles. Instead, child resistance is an empirically developed and verified closure mechanical property derived from closure testing with child subjects, as specified by regulations under the Poison Prevention Packing Act (PPPA). The authors report their longitudinal study of a specific Type III CR closure over a period of decades made with materials from different suppliers over time and using different injection molding tools. The study examines if the property of “child resistance” persisted and if it correlated with the mechanical specifications of the closure actually measured and controlled in the closure manufacturing process. This data is combined with the authors’ mechanical measurements of closure performance. Child resistance, being a complex, empirically tested property, cannot be regularly tested in the normal manufacturing environment. Despite minor manufacturing process and specification changes, if the mechanical specifications are appropriate (e.g. not intended to produce changes in CR mechanical properties) and with adequate quality control, the property of child resistance persists.