A product safety device is a piece of inline equipment fitted to a food production line to detect contamination or equipment faults before packed foods leave the factory. The most common examples are metal detectors, X-ray inspection systems, checkweighers, and magnetic separators, which screen for metal fragments, bone, glass, stones, or underweight packs at line speed. Many systems reject the suspect pack automatically and log the event for traceability. Because contamination can arise from worn machinery, broken screens, or raw-material impurities, these devices are calibrated and challenged with test pieces on a set schedule. They form part of the physical hazard controls within a HACCP plan, but they are a verification layer, not a substitute for good supplier control and preventive maintenance.